In this study we investigated a population of 175 seriously drug addicted patients. They were randomised in a controlled opiate maintenance program in Basel, Switzerland. We investigated hospitalizations in the time period three years before entry into the program and approximately 3.5 years after entry into this program. The mean age was 28.4 years, the mean drug injection time was 8.8 years. 82.6% of the patients were seropositive for HCV and 21.5% were HIV-infected. We observed 223 hospitalizations in 100/175 patients during the observation period of 6.5 years. Most commonly infections (n = 94), different diseases of internal medicine (n = 44) and surgical diseases (n = 41) led to hospitalization. Altogether, we found no decrease of the incidence of hospitalisations. However, there was a significant decrease of directly drug-induced diseases (p < 0.05). So far, hospitalizations did not diminish in this well-controlled opiate maintenance program. However, as shown in earlier studies, the incidence of HIV drastically dropped. Hence, it may be that a longer follow-up may prove beneficial regarding the incidence of hospitalisations.