In the course of a research program on tubular heat exchangers, pressure-drop and heat-transfer data are reported for heating and cooling a medium-viscosity oil flowing across banks of vertical tubes in seven test exchangers. The apparatus variables include equilateral triangle, in-line square, and staggered square arrangements; tube sizes of ⅜ in, and ¾ in. OD; and pitch ratios of 1.25 and 1.50. The results are shown both in simple plots of pressure drop and coefficient of heat transfer versus the rate of flow, and in generalized correlations. Tentative correlations are provided for friction and heat transfer which bring the data for these seven tube banks somewhat closer together than previous correlations. In a comparison of the heat-transfer coefficient versus pumping-power loss per unit surface area, the smaller diameter tubes at the smaller pitch ratio give the best performance.