Altogether 240 unselected intravenous drug addicts were tested for the presence of infection with delta virus (HDV). Anti-delta were found in 16 (16%) out of 100 drug addicts tested in the years 1988-1989 and in only one drug addict (0.7%) out of 140 tested in the years 1985-1986. It seems that delta virus has been introduced to Warsaw drug community in the mid-eighties and has spread enormously since that time.