Sand and granulated fertilizers were used as carriers in the preparation of granular formulations containing pirimiphos-methyl for the control of larvae of Culex pipiens molestus, Aedes cantans, Ae. vexans and Ae. sticticus. The formulations were prepared by adding 1 volume "Actellic' 50 EC (containing 50% w/v pirimiphos-methyl) to 50 volumes of carrier. Laboratory-determined LD99s for 4th instar Cx. p. molestus larvae were 4.0,1.2 and 2.0 g/m3 for granular formulations based on sand, ammonium nitrate and a combined fertilizer, respectively. LD100s determined in field conditions, ranged from 2-20g/m3 depending on the type of granular formulation, biotype, the instar and species of larvae. The effects of granules on non-target water fauna, e.g. Tubifex tubifex, Rhynchelmis sp., Mollusca, Turbellaria, Cyclops sp., Daphnia sp., Ostracoda, Asellus aquaticus, Hydrachna sp., Gerris lacustris, adult Dytiscidae, Helodidae (larvae), Dixella sp. (larvae), Chaoborus sp. (larvae) and Trichoptera (larvae) are discussed.