Nixons best-known work is the The Brown Sisters, a series of black-and-white portraits of his wife Bebe and her three sisters that he has taken each year since 1975. While the clothes, hairstyles and framing changes, there are certain continuities. Nixon always uses a large-format camera at roughly eye-level, mounted on a tripod, and the sisters always pose in the same order: Laurie, Heather, Bebe and Mimi.
The series has become a powerful essay on the passage of time, capturing the slow, incremental changes of the aging process. Other groups of work have included People with Aids (published 1991), a portrayal of people who are carriers of the virus and yet who are presented not as victims but as healthy and beautiful in appearance; and Family Pictures, in which Nixon records the growth of his children.