Purpose. The purpose of the study was to analyse the effects of age and gender in physiological responses, mechanics (stroke frequency, stroke length, stroke index), and performance time of master swimmers. Methods. Overall, 34 male and 25 female master swimmers were divided into 2 age categories: (a) 30-39 years, (b) 40-49 years, and completed a 100-m freestyle swimming test with maximum intensity. Stroke mechanics and performance time were measured during the effort. Blood lactate concentration was determined after the test in the 3 rd , 5 th , and 10 th minutes of passive recovery. Results. Two-way ANOVA showed no interaction between gender and age category for any examined variable (p > 0.05). Maximum blood lactate was maintained in both genders despite ageing (p > 0.05) and was lower for females compared with males (p < 0.001). Higher values were observed for stroke frequency, stroke length, and stroke index for males (p < 0.05). For both genders, the 30-39 years category had significantly higher values for stroke length (p = 0.020) and lower for stroke frequency (p = 0.014), indicating that these swimmers can produce stronger strokes than those in the 40-49 years category. Performance time values were significantly lower for males compared with females (p < 0.001), but did not change with ageing (p > 0.05). Conclusions. Despite ageing, swimmers are able to maintain all examined variables through a structured swimming training but with a possible decrease in stroke mechanics, independent of gender. Better values were observed for males compared with females probably owing to a greater muscle mass in the former.