For students and banks alike, this is an increasingly popular method of testing the water before taking the plunge.
Chris Bristow, head of the careers service at the London Business School, says: "Employers like internships because they offer an opportunity to evaluate someone over time. Students like them because they offer an opportunity to try out a career.
"Internships are a means of finding out what investment banking is really like."
However, before applying, it's worth bearing in mind that not all interns are equal. Known as 'summer associates', MBA interns are highly prized, and for this reason investment banks are unwilling to take a back seat in the recruitment process. Nearly two thirds of all summer associates are actively solicited.
If you're studying for an MBA at a "top" school and have expressed an interest in investment banking, the likelihood is therefore that you will have already been approached via the so-called "closed list" system. "We figure out who we like from the CV book and call them up," says Derek Walker, head of recruitment at Merrill Lynch.
In fact, banks do more than merely calling. At the London Business School, where 40% of MBA students go into investment banking, one bank took the entire first year of 270 students out to dinner.
Bristow says: "It's all about luring people and making them think about investment banking as a career."
Nadia Capy, global marketing manager for campus recruitment at Deutsche Bank, says: "Recruiting MBA students is a focused and personal approach."
Karen Paginton, her contemporary at Schroder Salomon Smith Barney, says: "We try to get to know students from day one. They have dinners and presentations and days out. We organised a trip up the river and a ride on the London Eye for people identified as good candidates."
Lavish attention of this kind is reserved for those studying at targeted schools. These are predominantly located in the US. European recipients of banks' attentions are most likely to be studying at Insead near Paris, or at the London Business School.
Nevertheless, even students at Insead, one of Europe's top business schools, are at something of a disadvantage when it comes to becoming summer associates. The MBA course at Insead, as at the vast majority of European schools, lasts for only one year.
Unlike those on two year MBA courses in the US, Europe-based students therefore lack the opportunity to spend a long summer with prospective employers.
However, there is an alternative. Professor David Norburn at the Imperial College Management School, says: "The substitute for the summer associate programme is the summer project." These projects are invariably linked to dissertations that contribute towards the MBA.
Although projects provide an opening, gaining an internship will nevertheless be harder if you are at a non-targeted school.
"Students at other schools must make a particular effort to come to our attention," says Richard Akhtar at ABN Amro. At one large US bank, the head of recruiting confesses that the main reason for accepting interns is to use them as a marketing tool at campuses that are strongly targeted.
"We hope that people will go back, talk to their friends about the summer, and encourage them to also make a full time application," he says.
However, around a third of places on structured summer associate programmes are available to 'open list' candidates, so applicants from schools beyond the firing range are in with a chance. Those actively seeking a place as a summer intern should apply before February, and in some cases significantly before.
Applicants whose credentials appeal will be subjected to multiple interviews. Particularly at the larger US banks, interviews are predominately behavioural, as opposed to technical.
"They find out quickly whether you are someone that wants to work there purely for financial rewards, or whether you're there because you're motivated by ambition and challenge," says one successful applicant.
Be prepared for questions such as why you applied to business school and what your motivations are, which may be repeated several times.
When the summer associate programme starts, it is up to both sides - banks and associates - to prove themselves. The onus is on associates to prove that they are competent, enthusiastic, motivated, and compatible with their team.
For their part, banks seek to portray themselves as places offering interesting deals, as rewarding and friendly places to work, and as places of fun. To this end, summer associates at Deutsche were treated to a "gruelling schedule of fun fun fun", including bowling, golf, karaoke, go-carting, and water-skiing.
Competition for high flying MBAs is such that banks regularly hold events for their own, and their rivals' summer associates. These are an opportunity to poach prospective employees.
But there is also hard work. Summer associates are treated as full time members of staff, to the point at which 13 or 14-hour days and 'all-nighters' are by no means unusual. Despite the fun, this is not a holiday.
Days begin early with breakfast meetings with high profile members of the bank. Nights end late and work is relentless when there is a deadline to be met.
However, the returns are good. As a summer associate you can expect to be paid in the region of 1,250 (E2,037) per week, plus additional perks such as free accommodation and a performance related bonus at the end of the programme. A high proportion of summer associates also walk away with an offer of a full time associate's position.
In many cases, testing the water proves tantamount to taking the plunge.