A 3-year (1992-94) prospective study of 1767 drug users from the Euregion Maas-Rhein evaluated a peer counseling intervention for reducing risk behaviors associated with HIV transmission. The HIV prevalence among drug users in this diverse Dutch, German, and Belgian area ranges from 10% to 30%. Duties of the paid peer counselors included promotion of HIV risk reduction in drug use and sexual behavior; administration of questionnaires; distribution of educational materials, condoms, and clean needles; identification of hidden subgroups in the target population; and the development of prevention materials. 50% of those reached by peer counselors had no prior contact with drug abuse services. Although drug users claimed syringes and condoms were readily available, high-risk drug and sexual behaviors were widespread. 52% were injecting drugs and 24.4% had traded drugs for sex. Condoms were used by 24.8% during sexual contacts with a main partner and by 73.5% during sex with casual partners. 47.8% of injecting drug users had shared their syringes with friends. Condom use was significantly higher among drug users residing in South Limburg, women, those over 30 years of age, and those with multiple sex partners. These findings suggest that existing HIV risk-reduction interventions such as methadone treatment and needle exchange may not be sufficient. More emphasis must be placed on personal skills training (e.g., assertiveness training) and peer-driven, lifestyle-oriented processes.