Non-invasive finger blood pressure has become a surrogate for central blood pressure under widely varying circumstances. We tested the validity of finger-aorta transfer functions (TF) to reconstruct aortic pressure in 7 cardiac patients before, during and after incremental bicycle exercise. The ARX model method was used for calculating finger-aorta TF's. Finger pressure was measured non-invasively using Finapres, aortic pressure using a catheter-tip manometer. When applying the individual TF's found during rest for reconstruction of aortic pressure (rAOR) during all workloads, systolic pressure was increasingly underestimated, with large variation between subjects: +4.0 to -18.1 mmHg. In most subjects diastolic pressure was overestimated: -3.9 to +5.5 mmHg. Pulse pressure estimation varied between +4.5 and -21.9 mmHg. In all cases wave distortion was present. Post-exercise, rAOR systolic error slowly declined and diastolic pressure was overestimated. During rest, the TF gain had a minimum between 3.65 and 4.85 Hz (Fmin). During exercise Fmin shifted to frequencies between 4.95 and 7.15 Hz at the maximum workload, with no change in gain. Post-exercise, gain in most subjects shifted to values closer to unity, while Fmin did not return to resting values. Within each subject aorta-Finapres travel time was linearly related to mean pressure (MAP). During exercise, Fmin was linearly related to both delay and heart rate (HR). We conclude that during increasing exercise rest TFs give an increasingly unreliable reconstruction of aortic pressure, especially at higher heart rates.