Jennifer Walters, the meek and mousy lawyer cousin of Bruce Banner, was the daughter of Sheriff Morris Walters. Agents of Nicholas Trask, a crime boss who had crossed paths with her father, shot and seriously wounded her on a day when her cousin was in town. Bruce gave her a blood transfusion, as no other donors of her blood type were available; the radioactive blood mutated Jennifer as it had her cousin, transforming her into the She-Hulk.
Although Jennifer was at first savage while in her form as She-Hulk, she eventually gained the same intelligence she had as the normal Jennifer Walters. She quickly came to appreciate the confidence and assertiveness that had come with being She-Hulk. For a long time, she felt more comfortable in her form as She-Hulk than in her "normal" form as Jennifer. But she has gradually grown comfortable in both forms, and realized that she has much to offer the world in both her forms. After a brief solo career, she joined the Avengers and temporarily replaced the Thing in the Fantastic Four.
During her tenure with the Fantastic Four, the She-Hulk had to prevent a radiation leak in a downed S.H.I.E.L.D. Helicarrier. This radiation exposure apparently mutated Jennifer to the point that she could not transform back into her original form. But this was an agreeable turn of events for her, since she preferred her She-Hulk form anyway. It was revealed much later that the "genetic block" was in fact purely psychological, shortly before a similar block locked her in non-Hulk form. That block proved to be temporary.
After the Fantastic Four , the She-Hulk rejoined the Avengers and joined the staff of District Attorney Blake Tower, where she met Louise "Weezi" Mason, formerly the Golden Age super heroine called the Blonde Phantom; during this period, she discovered that Mason had manipulated Towers into hiring She-Hulk so that Mason could again star in a comic book and thus avoid dying of old age. Mason's husband, also a former comic book character, had passed away three years ago, but other, more popular characters from the era, such as Captain America and Namor the Sub-Mariner, were still around.
While doing some legal work for Heroes for Hire, she also went on a few adventures with them and spent some time dating Luke Cage. Later She-Hulk was a member of the short lived hero group the Fantastic Force.
Jennifer currently works as a lawyer for the Superhuman Law division of the New York law firm of Goodman, Lieber, Kurtzberg, & Holliway. Now able to change forms at will again, Jennifer is rediscovering she sometimes has wildly different views and opinions in each form, where as the She-Hulk she has come out publically in favor of the recent Superhuman Registration Act, yet as Jennifer Walters she understands the views of those against the Act.