Radiations are known to cause behavioural perturbations like conditioned taste aversion (CTA), performance decrement, learning, etc., even at very low doses. The manifestation of radiation-induced behavioural degradation has not been understood well and requires further studies. Therefore, the effects of low-dose whole-body Co-60 gamma -irradiation in male rats were studied in terms of body weight and CTA learning. For CTA, the consumption of saccharin solution was considered as a parameter To protect against the adverse effects of radiation, Centella asiatica (aqueous extract) was tested and compared with ondansetron, a standard antiemetic drug. A dose of 2 Gy incurred significant body weight loss [t(9) = 9.00, P < .05] and induced CTA in rats [t(26) = 9.344, P < .01]. Administration of C. asiatica (100 mg/kg bw ip, 2 Gy, - 1 h) rendered significant radioprotection against radiation-induced body weight loss and CTA that became evident on the second postirradiation day [t(7)= 0 .917, P much greater than .05; t(7) = 4.016, P > .05]. Ondansetron (1 mg/kg bw) elicited higher degree of protection against CTA [t(7)= 3.641, P > .05] than C. asiatica [t(7) = 7.196, P > .05] on the first postirradiation day, but on the second postirradiation day, both were equally effective [t(7) = 3.38, P > .05; 1(7) = 4.01, p > .05]. In case of C. asiatica-treated animals, however, there was a consistently declining CTA from the second to the fifth postirradiation day whereas in ondansetron-treated animals it was inconsistent. Present investigation suggests that C. asiatica could be useful in preventing radiation-induced behavioural changes during clinical radiotherapy. (C) 2001 Elsevier Science Inc. All rights reserved.