The production costs of the larvicidal bacilli, Bacillus thuringiensis H14 and Bacillus sphaericus were worked out based upon the inputs used to produce them in a 13 litre working capacity laboratory fermenter. Whereas the production cost of one batch of B. thuringiensis H14 was US11.02 the production cost of B. sphaericus was US11.02 the production cost of B. sphaericus was US13.34. Also, the costs involved in controlling mosquito larvae in an area of one hectare with the bacilli and chemical larvicides were compared. The analysis showed that the cost of larval control with the bacilli was more or less equivalent to that incurred if fenthion was used, but significantly less than that incurred if malaria oil, paris green or abate was used.