Experiments were conducted to study the effect of various chemical and biological agents on stem canker caused by Botrytis cinerea Pers.: Fr. on tomato plants grown in sawdust under near-commercial greenhouse conditions. Lesion lengths following treatment with RootShield® and strain S33 of Rhodosporidium diobovatum Newell & Hunter, applied as post-inoculation sprays, were significantly smaller than those in inoculated controls. These treatments also increased fruit yield and decreased the number of dead plants compared with inoculated controls. Decree®, Prestop®, and R. diobovatum S33, applied as sprays, prevented the occurrence of stem canker and increased fruit yield in tomato. The number of dead plants was also smaller with these treatments than with the other treatments and in inoculated controls. These results suggest that, in tomato, post-inoculation sprays of RootShield® and R. diobovatum S33 can reduce lesion lengths, and that a preventive spray of Decree®, Prestop®, and R. diobovatum S33 might prevent stem canker, under near-commercial greenhouse conditions.Key words: biological control, Botrytis cinerea, Bacillus subtilis, Rhodosporidium diobovatum, grey mold.