Present paper is an attempt to investigate production performance, cost and return structure pertaining to broiler farming and undertake investment appraisal in terms of PBP, NPV, IRR and BCR. The cost and return analysis of different sizes of broiler farms in Sonitpur District of Assam has been carried out based on the primary data collected from 100 broiler farmers for the period from March 2012 to May 2012. The study revealed that average meat production per bird per cycle was 2.18 kilogram. Average cost of production per bird was ` 134.66. Total fixed and variable cost per bird was found to be ` 9.11 and  ` 125.55 respectively. On an average gross return and net return per farm per cycle were ` 374518.14, and ` 68702.59 respectively for the sample as a whole. There was a positive relationship between per bird net return and farm size which increased from ` 19.82 in Group I to ` 33.21 in Group IV. On the basis of NPV, BCR and IRR, investment in broiler farming was found to be most profitable in large sized farms, than smaller farms, although investment was economically paying in all the farms. Sensitivity analysis revealed that small sized farms were more sensitive to increase in cost and decrease in returns.