We investigated the effect of electively converting stable renal allograft recipients from cyclosporin A (CyA) to prednisolone and azathioprine on limb blood. We used a non-invasive method designed to measure the hyperaemic blood flow to the lower limb following a standard ischaemic insult. The hyperaemic blood flow was greater during CyA therapy--median 14 ml/100 ml tissue per minute (95% confidence limits 10.5-16.5)--than that after conversion--median 11 ml/100 ml tissue per minute (8.3-13.8; P less than 0.01). By increasing peripheral vascular resistance and reducing limb blood flow, CyA may have caused an increase in the degree of ischaemia, so resulting in a greater hyperaemic response.