Experiments evaluating the bio-control of the cabbage root maggot, Delia radicum, with entomopathogenic nematodes were conducted in the greenhouse and in the field. In the greenhouse better control was obtained with Steinernema feltiae than with S. arenarium, S. carpocapsae, Heterorhabditis megidis, and H. bacteriophora. Increasing doses of S. feltiae improved insect control; the best results were obtained with applications of 4,000 or 8,000 infective juveniles per plant. Applying S. feltiae eight days earlier or eight days later than the inoculation of insect eggs or applying both at the same time did not give significant differences in D. radicum control. Field control of D. radicum with S. feltiae was not successful in early spring but improved in summer. The number of surviving insects and the cabbage damage were significantly reduced after applying S. feltiae in summer.