Multiproduct firms constitute a considerable share of firms and account for an even greater share of production. Nevertheless, the vast majority of production function estimates are based on the assumption that firms are single-product manufacturers. This assumption is due to a lack of data on how firms allocate their inputs across their various product lines. I provide a strategy for estimating product-specific input allocations and production functions of multiproduct firms involved in monopolistic competition. The strategy is based on using firms’ product prices and output demand in solving for product-level input allocations.