The aim of this study was to investigate the relation between free testosterone (FT) level and basic cognitive functions in older men. Three cognitive computer tasks were aimed to measure visual-processing speed, ability to suppress inappropriate responses, and visuospatial cognition, respectively. The tasks employed were a visual backward masking task, the Eriksen flanker task, and a mental rotation task. Participants were 72 older men (mean age = 67.2 years, range 57-79). The influence of FT; age, alcohol consumption, and education on task performances was examined by means of multiple linear regression analysis. FT level was positively associated with accuracy on the short intervals (33 and 50 ms) of the backward masking task and negatively with response latency on congruent flanker-task trials. These results indicate faster visual-processing speed in older men with higher FT levels. FT level was positively associated with interference elicited by irrelevant incongruent flankers, which implies that older men with higher levels of free testosterone exert less inhibitory control. Consistent with previous research, higher FT levels were associated with faster 'same-different' responses for unrotated mental rotation stimuli, but not with the slopes of the response time rotation functions. Older age was associated with tower backward masking accuracy at 33 ms and with lower overall mental rotation accuracy. Higher education level was associated with faster processing speed for congruent flankers and with higher overall mental rotation accuracy. Alcohol consumption did not affect the task performances. Our results suggest that higher FT levels in older men may promote sustained visual-processing speed and visuospatial ability, probably at the expense of some inhibitory functioning. (C) 2008 Elsevier Ltd. All rights reserved.