I evaluated the acceptability of three anticoagulant rodenticides {warfarin, brornadiolone and flocoumafen) by the roof rat, Rattus nittus, using Acceptability-index calculated by the following formula: A-index={(X-Y)!{X+Y)} × 100, X= average intake <g/dayfkg) of poison bait, and Y=average intake of blank bait, The average A-index in bromadiolone (50 ppm) mixed with sunflower seeds and sesame oil was O.5 in comparison with the blank bait and the resultant mortality was 1OO%. This value of the

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... dex was the highest of all three rodenticides. The index in fiocoumafen (50 ppm) was -42.2, which was small but the mortality was as high as 70%. The indexes in warfarin (250 ppm) mixed with seeds and oil, and warfarin (50 ppm) were -52.9 and -37.1, respectively. Both of these values in warfarin were small and the mortalities were O%. The index in warfarin {250 ppm) without seeds and oil was -65,2, which was the smallest of all test samples, though the mortality was 20%. Therefore, bromadiolone and flocoumafen are promising agents for the control of roof rats in Japan.