For annular-sector ducts, steady, laminar, and constant-property forced-convection flow and heat transfer in the entrance region have been analyzed numerically using a general, marching procedure. Two types of thermal boundary conditions have been considered: (1) uniform temperature both axially and peripherally (T boundary condition); (2) uniform axial heat flux with uniform peripherally temperature at any cross section (H1 boundary condition). Numerical analysis has been conducted in the following range of parameters:Di/Do= 0.00, 0.25, 0.50, apex angle of the sector 2 alpha = 18 degrees, 20 degrees, 24 degrees, 30 degrees, 40 degrees, and Pr = 0.707. The solutions of the developing Nusselt number and friction factor are presented as functions of nondimensional axial distance. Comparisons are made between the computed results and the analytical or numerical results available in the literature. For all cases compared, satisfactory agreement is obtained.