Constraints in adoption of biological inputs usage in cotton cultivation of Tamil Nadu have been identified. Among the reasons for non-adoption of bio-inputs, long-term practice has been considered as the important factor by the non-adopters (mean score, 67.18) and lack of adequate extension as the second important factor (mean score, 62.15). The probability of adoption of bio-inputs has been estimated by the multinominal logit model which has been found significant at one per cent level, based on the log-likelihood ratio test. The model has correctly predicted 78 per cent of the adopters and non-adopters. The analysis has indicated that the farmers’ perceptional characteristics are positively and significantly related to the adoption of bio-inputs, whereas storage and handling is negatively related to the adoption. Among the suggestions for enhanced bio-inputs usage, extension of subsidy has been considered as the prime suggestion by the farmers (mean score, 66.21). Cotton crop has inelastic calendar of operations, and the pest management operations are highly time bound and any delay in the availability of biological inputs would seriously hamper its adoption. Hence, the timely availability has been regarded as the second important suggestion by the farmers (mean score, 63.75).