Methyl parathion mixtures with pyrethroids were tested in large and small plots in several states to evaluate increased efficacy against the cotton aphid (Aphis gossypii Glover). Results indicate the addition of methyl to most pyrethroids tested improves control of aphids on cotton. This additive effect ranges from 9 to 50 percent which varies according to geographic area. The combination of ethyl-methyl parathion performed well against aphids in Texas. The mixture Thiodan-methyl parathion continues to be among the best treatments against aphids in most cotton states.