A number of 1-(2-aminopropyl)-2-mercaptobenzimidazoles related to the TIBO derivative R82150 have been prepared and tested for their activity against human immunodeficiency virus type 1 (HIV-1). These compounds were all modest inhibitors of the cytopathic effects of HIV-1 in vitro, but only very weak inhibitors of HIV-1 reverse transcriptase (RT).