AbstractThe stability of three synthetic pyrethroids (cypermethrin, deltamethrin and permethrin) to selected tributyltin compounds, Bu3SnX [where X = OSnBu3, Cl, O2CC6H5, O2C(naphthenyl), OSO2C2H5], (Bu3SnO)3PO and (Bu4N) (Bu3SnCl2), in toluene solution was investigated by infrared spectroscopy over a 24‐week period. It was found that only (Bu3Sn)2O reacted with the pyrethroids and that their order of reactivity was cypermethrin>deltamethrin>permethrin. An attempt was made to elucidate the reaction mechanism(s) occurring between (Bu3Sn)2O and the pyrethroids by studying mixtures of this tributyltin fungicide with simple model compounds, R1CO2R2where R1=CH3; R2=CH2C6H5and R1=cyclo‐C3H5and R2=CH2C