A study is reported on haematological alterations in buffalo calves from subchronic oral exposure to the pesticide fipronil, sodium fluoride alone, and the two in combination. Twenty-four male buffalo calves, 6 to 12 months old, were divided into 4 groups of 6 animals each. Group I without treatment served as the control. Groups II and III were orally administered commercial fipronil at 0.5 mg/kg bw/day and sodium fluoride (NaF) at 6.67 mg/kg bw/day, respectively, for 98 days. An additional group IV was co-administered fipronil and NaF at the same dosages as groups II and III. Although blood haemoglobin and total erythrocyte count were not appreciably altered by fipronil alone in group II, they were lowered by NaF in group III and in the combined group IV. On the other hand, total leukocyte count increased in the NaF group III and in the combined group IV but not in the fipronil alone group II. The present study indicates that fipronil aggravates the toxic effects of NaF on the hematopoietic system as haematological alterations were more pronounced with concomitant exposure to fipronil and NaF.