A concentration of 1.2 mg/l of aluminum phosphide (phostoxin) applied for 8 or 12 h to infested kola nuts completely killed the larvae, pupae and teneral adults of the kola nut weevil. Length of exposure period to phosphine and time after fumigation was found to affect significantly the susceptibility of the developmental stages. Chemisorption was inferred from the resultant development of a blue taint that persisted for 3 days in over 70 per cent of the freshly harvested trial nuts fumigated with phosphine at a high moisture content of 50-59%.