AbstractA number of antitumor‐active octahedral organotin complexes of the type R2SnX2L2, where R=ethyl or phenyl, X = chloride or bromide, and L2= o‐ phenanthroline or 2‐(2‐pyridyl)benzimidazole, have been shown to exhibit in vitro antiherpes activity towards both herpes simplex virus types 1 and 2 (HSV‐1 and HSV‐2). In addition, a series of mono‐, di‐, and tri‐organotin halides (alkyl and phenyl) demonstrated weak antiherpes activity in the same viral assay system. Selectivity indexes for the tin compounds were calculated and compared with those available in the literature for a number of well‐characterized and commercially important antivirals, e.g. adenine‐9‐β‐D‐arabinofuranoside (ara‐A), cytosine‐β‐D‐arabinofuranoside (ara‐C), 5‐iodo‐2′‐deoxyuridine (IDU) and 9‐(2‐hydroxyethoxymethyl)guanine (acyclovir, ACY). Although the organotin complexes are less effective in vitro than either ACY or IDU, as determined by their selectivity indexes, they are comparable in activity with both ara‐A and ara‐C in this particular assay. With few exceptions, most notably (C2H5)2SnBr2(o‐phen), the organotin compounds examined in this study are more active against HSV‐1 (F strain) than HSV‐2 (MS strain). The results presented here represent the first study