The efficacy of various biological control agents and their application methods was tested against the root-knot nematodes Meloidogyne javanica and Meloidogyne incognita in large, in-ground tomato production areas. Treatments included infective juveniles (IJs) of the entomopathogenic nematode Steinernema feltiae, nematode infected insect cadavers and cell-free supernatant of the nematode's bacterial symbiont (Xenorhabdus bovienii) and the nematode-parasitic fungus Purpureocillium lilacinum. The treatments were tested in two 1000 m(2) greenhouses, one located in Fethiye and the other in Kepez Turkey. Galling index according to the Zeck scale, total yield and cost analyses were evaluated for each application method. The Zeck scale was the lowest (mean index = 2.37) for plants treated with a commercial product based on P. lilacinum, followed by S. feltiae (125 IJs/cm(2)), X. bovienii (dipping + topical application) and cadaver treatments. The control group had the highest root knot infection (mean index = 8.55). Total yield from the P. lilacinum-treated plants in the Kepez region was estimated at 18.800 kg/1000 m(2), which was the highest yield among all treatments in both regions. S. feltiae and S. feltiae cadaver application treatments followed the P. lilacinum treatment with 17.216 and 16.440 kg/1000 m(2) production, respectively. Total yield was 11.184 kg/1000 m(2) in the control. The cost analysis of each treatment was calculated based on the total harvested amount of tomatoes per plant x 4000 (the number of tomato plants in a typical 000 m(2) greenhouse). The net profit difference between P. lilacinum treated and non-treated (control) greenhouses in Fethiye and Kepez regions was US $ 3268 and 797 US $ for the tomato growers per 1000 m(2), respectively.