A three-dimensional numerical investigation of steady laminar flow and heat transfer is undertaken to determine the developing as well as fully developed temperature fields. Physical interpretation is given for the enhancement of the heat transfer coefficient at the thermal entrance region and the overall increase in heat transfer in helical ducts compared to straight ducts. The variation of peripherally averaged Nusselt number is studied for the constant wall temperature boundary condition. Detailed analysis is given for the peripheral variation of Nusselt number and the temperature field at different cross-sectional planes. The effect of the Prandtl number on the temperature field is also studied. The problem is solved using a segregated solution approach which reduces the total computer memory requirements.