Plant parasitic nematodes such as root-knot nematodes (RKNs) are a major threat to vegetables, fruits and ornamental plants which cause yield loss. One of the best alternative methods of nematode control is using the entomopathogenic fungi (EPF). The aim of this study was to evaluate the effects of two Turkish isolates of entomopathogenic fungi, Beauveria bassiana (Bals.-Criv.) Vuill. (F-56 and F-63), against naturally infected mixed populations of Meloidogyne incognita and Meloidogyne javanica on tomatoes under natural conditions. The experiment contained 3 conidial suspensions (10(6), 10(7) and 10(8) cfu ml(-1)) with 4 replicates of each treatment. A total of 32 plants were arranged in a randomized block. EPF were applied 4 times (15 days before planting, planting, 15, and 30 days after planting). Nematicide [Paecilomyces lilacinus strain 251 (BioAct (R))] was used as a positive control. At the end of the growing season, the efficiency of the applications was determined according to the root gall index (I) and yields of tomatoes (II). The fungi concentration of 10(8) cfu ml(-1) was significantly greater than in the others. This concentration from both isolates [F-56 (4.59 +/- 0.54) and F-63 (2.77 +/- 0.59)] controlled M. incognita and M. javanica and increased the yield of tomatoes. The results demonstrated the suitability of using B. bassiana isolate F-56 and F-63 for reducing RKNs on tomatoes under greenhouse conditions.