To examine the prevalence of psychostimulant dependence and the characteristics associated with nonmedical users' development of dependence.The study sample was drawn from the 1995 to 1998 National Household Surveys on Drug Abuse. Statistical analysis was conducted on a total of 1047 individuals aged 12 or older who reported nonmedical use of stimulants in the past year. Multiple multinomial logistic regression identified factors related to stimulant dependence and dependence problems.Among all past year stimulant users, 19% met criteria for stimulant dependence in the past year, and an additional 16% reported having one to two dependence problems. Adjusting for demographics and drug use characteristics, female stimulant users were an estimated 2.6 times more likely than male users to develop dependence. Not only did the Western region of the United States have more recent stimulant users than other regions, its users also were more likely to meet criteria for dependence or experience dependence problems. Stimulant users who had increased odds of progressing into dependence were characterized by an early onset of stimulant use, coexisting multiple illicit drug use, and an onset of daily cigarette smoking between the ages of 13 and 17 years.Gender differences in initial stimulant use and progression to dependence require further investigation, including contextual, cultural, or perceptual factors related specifically to the choice of drugs by females.