Cotesia plutellae Kurdjumov was evaluated as a potential biological control agent for diamondback moth, Plutella xylostella (Linnaeus), in cabbage in spring 1993 and 1994. The parasitoids were reared in a commercial insectary in Texas, delivered overnight via air express, and released 24-48 h after receipt in cabbage fields in Northeast Florida. In 1993, only adult parasitoids were released, but adults and cocoons were released in 1994. The numbers of C. plutellae released ranged from 456 per ha per wk in 1993 to 1,334 per ha per wk in 1994. Four consecutive releases were made each year beginning in early February. Parasitism of diamondback moth larvae by C. plutellae ranged from 3.6 to 10.9%, and the level of parasitism was related to the total numbers of parasitoids released. C. plutellae parasitoids were complimentary to the naturally occurring parasitoid Diadegma insulare (Cresson), and the combined mean seasonal parasitism of diamondback moth exceeded 34% in some fields. There was no evidence that C. plutellae became established in the general area although gt 124,000 parasitoids were released over the 2-year test period.