We analyzed ventilation-induced changes in arterial blood pressure and photoplethysmography from waveforms obtained by monitoring 57 patients in the operating room and intensive care unit. Analysis of systolic and pulse pressure variations during positive pressure ventilation, DeltaUp, DeltaDown, and changes in the preejection period on both arterial and photoplethysmographic waveforms were possible in 49 (86%) patients. The pulse pressure variation and preejection period were similar when calculated using both arterial blood pressure and photoplethysmography, whereas the other variables were different. Photoplethysmographic pulse variation >9% identified patients with arterial pulse pressure variation >13% (area under ROC curve = 0.85) or DeltaDown >5 mm Hg (area under ROC curve = 0.85). In hypotensive patients, photoplethysmographic pulse variation >9% remained the best threshold value (pulse pressure variation >13%: area under ROC curve = 0.90; DeltaDown >5 mm Hg: area under ROC curve = 0.93) for predicting fluid responsiveness. In conclusion, this study showed that pulse variations observed in the arterial pressure waveform and photoplethysmogram are similiar in response to positive pressure ventilation. Furthermore, photoplethysmographic pulse variation > 9% identifies patients with ventilation-induced arterial blood pressure variation that is likely to respond to fluid administration.