The main purpose of the present study was to examine the relationships between measures of fitness [estimated peak oxygen consumption (V(O2) peak) and handgrip strength] and forearm vascular function in 55 young (22.6 +/- 3.5 yr) adults. In addition, the present study considered methodological and technical aspects regarding the examination of the venous system using mercury in-Silastic strain-gauge plethysmography (MSGP). Forearm venous capacitance and outflow were examined using five different [7, 14, 21, 28, and 35 mmHg < diastolic blood pressure (DBP)] venous occlusion pressures and after a 5- and 10-min period of venous occlusion. A pressure of 7 mmHg < DBP and a period of 10 min venous occlusion produced the greatest (P < 0.05) venous capacitance and outflow, without altering arterial indexes. Reproducibility of forearm arterial and venous indexes were evaluated at rest and after 5 min of upper arm arterial occlusion at 240 mmHg on three different occasions within 10 days with the interclass correlation coefficient ranging from 0.70 and 0.94. Estimated V(O2) peak correlated with postocclusion arterial inflow (r = 0.54, P = 0.012) and resting venous outflow (r = 0.56, P = 0.016). Finally, handgrip strength was associated with venous capacitance (r = 0.57, P = 0.007) and outflow (r = 0.67, P = 0.001). These results indicate that the examination of forearm vascular function using MSGP is reproducible. Moreover, the data show the importance of careful consideration of the selection of venous occlusion pressure and period when implementing these measures in longitudinal trials. Finally, the associations between fitness and venous measures suggest a link between venous function and exercise performance.