Aims: This study assessed the prevalence of substance use among Iranian patients with nephrologic disease (chronic renal failure) who were admitted in different nephrologic wards at Shiraz general hospitals. Design: Cross-sectional survey using structured interview and also using DSM-IV criteria for substance dependency. Setting: General hospitals in Shiraz city (patients with nephrologic disease admitted in different nephrologic wards). Participants: 64 (32 men and 32 women) patients selected randomly. Findings: Data were gathered by a structured interview from 64 patients admitted in nephrologic wards of general hospitals in 2001. The mean age was 49.39 years (SD = 19.62) ranging from 18 to 80 years. 26 (40.6%) of the subjects (65.6% of the men and 15.6% of the women) reported the use of substance(s) once or more in their lives. The majority, 23 (35.9%) used tobacco, 9 (14.1%) used opium and 2 (3.1%) used alcohol. None had used cannabis, heroin, cocaine or LSD. 20 (31.3%) of the subjects (50% of the men and 12.5% of the women) were currently substance dependent, using DSM-IV criteria. The majority, 18 (28.1%) were nicotine dependent, and 6 (9.4%) were opium dependent. There was a nonsignificant relationship between income or occupation or education and prevalence of substance use. The reported reasons for initial use of substance(s), in order of frequency, were enjoyment, modeling and release of tension, and also for current users were, habit, enjoyment and need. Conclusions: Substance use especially cigarettes, opium and alcohol was found to be high among patients. There was no report of cannabis, heroin, cocaine or LSD use. Cultural attitudes toward substance use were found to affect the type and amount of use. These findings can be considered when planning preventive or therapeutic programs.