The effect of natural enemies on the tomato moth larvae was studied, at La Platina Research Station (INlA), Santiago, Chile, giving special emphasis to the action of the ectoparasite D. phthorimaeae. The effect of the natural enemies was determined weekly, by collecting 100 tomato moth larvae from a plot (0.12 ha) with tomato (var. ACE 55 V.F.), free ofchemical pesticides. The highest natural mortality reachedwas about 50%. From this, an average of 39.5% was due to the action of D. phthorimaeae, suggesting that this species is the most effective natural enemy of the pest, in the central zone of Chile. It was also determined that a granulosis virus is an important moth mortality factor.