Cabbage is cultivated worldwide and other cruciferous crops are also widely present in various regions. Thought to be of palaearctic origin and imported into newly colonized countries by European immigrants, the plant was however accompanied by an important pest which now has a cosmopolitan distribution: the diamondback moth (DBM), Plutella xylostella (L). Its economic importance can be appreciated through the number of papers consecrated to it. During the last 20 years and according to the Review of Applied Entomology (RAE), 1937 papers dealt with this moth. Oddly, while papers dealing with insecticides and Bt (Bacillus thurengiensis) resistance and applications are numerous, those concerning parasitoids are fewer than expected. Does this mean that there is a lack of interest in biological control over this time? The aims of this chapter are to review current Hymenopteran parasitoid taxonomy, the problems faced when using Hymenoptera as biological control agents and future perspectives.