This empirical study on factor substitution and technical change in Bangladesh agriculture uses the translog cost function which belongs to the family of flexible forms and does not a priori restrict the value of the elasticity of substitution. Using the function, both substitutability and complementarity relationships between inputs are found in Bangladesh agriculture. Most of the own elasticities of demand for farm inputs are found to be less than one. There are also evidence of land and labour saving technical changes and presence of fertiliser and irrigation using technical changes.