The use of the formamidine miticide amitraz in cotton past management was investigated in tests using eggs and first instar larvae of the tobacco budworm. Ovicidal activity of amitraz was very low against eggs of susceptible and resistant tobacco budworm. Toxicity of amitraz and chlordimeform was also low against first instars. Piperonyl butoxide greatly increased amitraz toxicity to larvae of both strains and synergized chlordimeform much less. Both formamdines synergized cypermethrin. Chlordimeform synergism of cypermethrin was greater than amitraz synergism for both susceptible and resistant tobacco budworm larvae. Piperonyl butoxide synergism of cypermethrin:formamidine combinations increased toxicity to resistant larvae and decreased toxicity to susceptible larvae.