Comparative tests in Alaska of (a) a thickened NH4 phosphate liquid fire retardant (Phos-Check 202) and (b) two liquid concentrate retardants (Fire-Trol 930 and Fire-Trol 934) showed that (b) can be successfully dropped by tanker aircraft on the Alaskan type of forest fuel, but their use may be limited by transport costs and problems of summer and winter storage. Development of an adequate colouring agent would greatly enhance the value of (b) under Alaskan conditions.