Results of small plot insecticide evaluation trials published in Insecticide and Acaricide Tests (except for 1990 data) were evaluated for efficacy trends within classes of insecticide. Pyrethroid efficacy was negative in 1985 but was nearly equal to that of organophosphate insecticides during 1988-89. Pyrethroid efficacy is attributed to the advent of later generation pyrethroids. Efficacy of all compounds was low during 1988 and there was a general downward efficacy trend for organophosphates and pyrethroids from 1986 to 1990.