BACKGROUND There has been a surge of heroin abuse in Taiwan in recent years making it necessary to study and understand the characteristics, drug use patterns and behavior among heroin users. METHODS Two hundred and eighty-three patients hospitalized for heroin detoxification received a diagnostic interview and a semi-structured interview which rendered the demographic information, medical history, and patterns of and reasons for heroin use. Differences between male and female drug users were also compared. RESULTS More than half of the subjects (54.3%) were unemployed. The percentage of unemployment of female patients was significantly greater than that of male patients (75.9% vs. 48.0%, p<0.05). Women were significantly younger (p<0.001) and had a significantly earlier (p< 0.001) onset of heroin use than men. About one-third of the subjects (33.9%) were multiple drug users, with amphetamines as the most common (79.2%) concomitant drug of abuse. More men reported curiosity as the reason for first use, while more women reported peer influence as the reason for first use. CONCLUSIONS This study showed that significant gender differences in employment status, age of first use, and reasons for drug use among heroin addicts. Further exploration of gender and cross-cultural differences could have important theoretical and treatment implications.