Onion production in New York State is primarily limited to the geographically diverse muck soil areas. Varying degrees of difficulty have been encountered in controlling Hylemya antiqua (Meigen) in these areas because of dissimilar cultural practices and climatic conditions. The standard control insecticides are diazinon, fensulfothion and fonofos, but only fonofos provides adequate protection in some areas. Nine trials conducted at 4 locations over a 3-yr period indicate that the candidate materials carbofuran, chlorpyrifos, CGA 12223, (0-[5-chloro-1-[ 1-methylethyl]-1 H-1, 2,4-triazol-3 yl]0-0 diethyl phosphorothioate), N2596, (S-(p-chlorophenyl) O-ethyl ethylhosphonodithioate), Oftanol® (Bay SRA 12869), (2-(ethoxy-((1-methylethyl) amino)phosphionthionyl)-oxy)benzoate), and terbufos provided equal or better protection than the best standard materials.