Perceptions of knowledgeable Bangladeshi farmers regarding rice yield losses due to various technical constraints were studied to quantify the magnitude of yield losses and yield gaps. Two model farmers were chosen from each of the selected 120 thanas of the country. These 240 sample farmers were interviewed to solicit their perceptions on probability of occurence of different biotic and abiotic constraints, the proportion of area affected by these constraints and the corresponding yield losses. The result on normalized yield loss estimation shows that abiotic factors are much more severe than the biotic ones in constraining rice yields irrespective of production ecosystems. Yield loss from all biotic and abiotic constraints is estimated at 0.8 tons ha-1 which is about 28% of the current farm level yields. The volume of rice production lost from these constraints is estimated at 7.8 million tons of paddy valued at US $ 1558 million at the existing international prices. Ex-ante analysis shows that the research investment on the priority problem areas would pay fairly lucrative returns to the government.