The conductive cooling of new oceanic lithosphere causes both horizontal and vertical contraction. Along transform faults and fracture zones, the contraction of material on each side of the fault leads to differential subsidence since juxtaposed seafloor of different ages subside at different rates. Horizontal contraction causes accumulation of thermal bending stresses, which are partly relieved by flexural bending along the transform. The relative vertical motion implied by plate flexure at the transform is more important than that predicted by differential subsidence; when combined this net vertical slip rate may exceed 5% of the full spreading rate for slow spreading ridges. The high vertical to horizontal slip ratios implied may explain anomalously high subsidence rates for seafloor in the proximity of ridge-transform intersections. Departure from horizontal strike-slip inferred from transform fault focal mechanisms may possibly be used to put additional constraints on the isotherm controlling the transition from brittle to ductile failure in the oceanic lithosphere. ¿American Geophysical Union 1990