Five pools containing immature stages of Anopheles punctulatus were treated with pyriproxyfen at 4 different dosages. Inhibition of adult emergence was observed in pupae collected from the test pools and/or those obtained by rearing of the 4th instar larvae. Adult emergence was inhibited completely for 2 months at a dosage of 0.1 ppm, for one month at 0.05 ppm and 0.01 ppm, and for 20 days at 0.02 ppm. Death of test insects were observed at the pupal stage and at adult emergence. The mortality rate at adult emergence increased with the duration of larval rearing and with the elapse of time after application.