The width of the articular space of the acromioclavicular (AC) joint was investigated to evaluate normal range values and any possible variations in relation to age and sex. Radiographs of the AC joints of 72 males and 28 female (age range: 38-83 yrs) were studied. The articular space width of the AC joint was measured using a semiautomatic computerized system. The measurements were performed bilaterally at the level of smallest distance between the articular surfaces in all the radiograms. The mean value of the articular space width was calculated for all the subjects as a single group, for that of the males and for that of the females. The films were then divided into four groups according to age (< 50; 50-59; 60-69; > 70 yrs) and the mean value per group was calculated. The values obtained were studied using variance analysis. No significant difference were found in the mean values of the articular space width when males and females were compared as regards to age. However, even if the articular space width diminished, in both sexes, with an increase in age, the differences between age classes were not statistically significant.