In special cases of crossflow the mean overall heat-transfer coefficient can be calculated, when either only laminar length effects or only temperature dependences are present. With one laminar stream the mean value can be calculated as for cocurrent and countercurrent flow and the result is valid for any flow arrangement. For the case of two laminar streams a solution is presented which is valid for any crossflow arrangement. For only temperature-dependent heat transfer and crossflow with only one row a special method is presented. According to this method heat transfer must be calculated at two points if it depends only on the fluid temperature inside the tube, and at four points if it is a function of both fluid temperatures. Further, a more general approximation method is described for the calculation of the mean overall heat-transfer coefficient and the overall pressure drop, which is valid for any flow arrangement and combined length and temperature effects. This approach was developed from a previous pure counterflow method; the heat transfer and pressure drop must be calculated at two points. The general method was tested with examples for which reliable solutions (special crossflow cases and cocurrent flow) are available and very good agreement was obtained.