The biology of Hellula undalis on cabbages was studied in the field and in the laboratory in Turkey. In the laboratory, at 25-29'C and 50-60% RH, the adult lifespan was about 4.43 days, the number of eggs per female about 153, the number of larval instars 5, and the duration of the larval, prepupal and pupal stages 11.03, 1-3 and 6.8 days, resp. In the field, where light traps were operated at 2 localities, the adult flight began in mid-July and increased to maximum levels in August and October. Larval damage was observed first in cabbage nurseries and then in fields of older plants. Larval population peaks occurred in August and September and larval feeding continued up to November, depending on the situation of the plants. Braconid, ichneumonid and chalcidoid parasitoids were recovered from the larvae, and Diptera from the pupae. none