A field trial of Bacillus thuringiensis serotype H-14 has been done in Rawasari, Jakarta. Bacillus thuringiensis serotype H-14 under the trade-name of Sandoz 402 I in wde formulation and under the trade-name of Bactimos in wdp formulation is a specific agent against mosquito larvae (WHO mimeo. series, 1980). The result of the trial showed that both formulations have a short killing effect, not more than one day against the larvae of Culex quinquefasciatus in Jakarta, Indonesia. Bactimos wdp has a better killing effect against early instar larvae as compared to Sandoz wdc.