The physiological characteristics of 32 elite Canadian synchronized swimmers were studied. The variables examined included aerobic power (VO2 max), anaerobic power measured by a maximal 30 second effort on a bicycle ergometer (AN30) and pulmonary function including forced vital capacity (FVC) and forced expiratory volume in one second (FEV 1.0). As a group, they were superior to non-athletic (untrained) women in VO2 max, with a mean of 44.4 ml . kg-1 . mon-1 or 2.39 l . min-1 but lower than competitive women swimmers of similar age. FVC and FEV 1.0 values were also higher than non-athletes and lower than competitive swimmers. AN30 was unremarkable, being identical to that of non-athletes. Comparisons were made between junior and senior competitors and between the 2 senior teams that made up the Canadian national team. Correlations between the athletes' performance scores in the 1977 Canadian national championships and VO2 max, AN30, FVC amd FEV 1.0 failed to yield any significant relationships. However, VO2 max in ml . kg-1 . min-1 related to solo performance scores was very close to the accepted level of significance (r = .41, p = 06). Precision techniques and skills are undoubtedly of major importance in this sport. However, a level of aerobic power sufficient to prevent fatigue during a performance and to allow long hours of training on technique would be prudent.