Think summer internships are only for college students? Think again. Some of the big investment banks are bringing in adult interns for retraining.

Morgan Stanley has a program called Return to Work at its offices in New York, London, Hong Kong, and Mumbai.

Morgan Stanley's Peg Sullivan, the global head of talent management, says the program has allowed her company to creatively reach an untapped pool of talent. Sullivan says the participants in Return to Work bring an incredible amount of enthusiasm and are like campus hires but with real work and life experience. Ideal candidates for these programs are looking to get back into fields where they've already worked, but have been out of the game for a few years, often raising kids or caring for aging parents.

Credit Suisse's Lisa Monaco, the Real Returns Program manager, says individuals in the program have a proven track record and are able to bring skill sets from their previous career back with them.

Jennifer Kelley is an intern with Real Returns. She says her participation has been a great way to come back and prove that she can still make a professional impact.

Goldman Sachs' Return-Ship program takes about 20 interns per class.

MetLife's Act Two internship lasts about 10 weeks.

MetLife Chief Technology Officer Jim O'Donnell says that Act Two had 13 interns and hundreds of applicants in its second year. O'Donnell calls the program a home run for his company.

Many of these internships, including JPMorgan Chase's Re-Entry Program, are try-outs for full-time jobs.

JPMorgan Chase Managing Director Julie Lepri says the company is hoping that these interns are the right match for the company and that the job JPMorgan Chase is offering is the job that person wants. The internship is a great opportunity to test that out.

Do you think a midlife internship could work for you? Have a solid resume and be ready to rock and roll.

Lepri says looking JPMorgan Chase is looking for assertive problem solvers who are willing to learn, take initiative, and ask questions.

Many adult internships are well-compensated. At the big banks, both college interns and midlife interns are often paid comparable salaries to those of entry-level full-time employees.

--ALISON MORRIS