Laminar forced convective heat transfer in a two-dimensional 90° bifurcation is studied numerically. The governing elliptic equations are solved by a finite-difference numerical scheme utilizing primitive dependent variables. A wide range of Reynolds numbers and dividing flow rates is studied with air at constant properties as the working fluid, which is heated by the constant-temperature walls of the bifurcation. The locations of the separation and reattachment points corresponding to the two recirculatian zones that form in the bifurcation are quantified as a function of the Reynolds number and dividing flow rate. For a given dividing flaw rate, the sizes of the two recirculation zones increase as the inlet Reynolds number is increased. On the other hand, for a given Reynolds number, the sizes of the two recirculation zones increase as the dividing flow rate increases, but they reach maxima after which a higher dividing flow rate results in smaller recirculation zones. The variation of the local Nusselt number along the walls of the bifurcation is discussed in light of the direct effects of the highly perturbed flow field. The prevalence and extent of the false diffusion for this geometry are also examined. Excessive false diffusion is observed in regions where the velocity vector is not aligned with the computational grid.