Serial fitness testing using a cycle ergometer and a submaximal work-load technique was performed monthly on 22 expeditioners at Davis Station, Antarctica, during the period February 1982 to January 1983. The results showed a linear increase in fitness in the group over the 12 month study period, including the winter period when outdoor activities were limited. The regression equation for fitness (measured as maximum oxygen uptake) was VO2max (ml . min-1 . kg-1) = 43.96 + 0.631 (time) where time is the month number from 1 through to 12. The correlation coefficient of the regression line representing fitness plotted against time in months was 0.918 (p less than 0.001). It is evident that indoor station activities and limited outdoor activities were more than adequate to maintain physical fitness in the winter period. Pre-departure fitness assessment for expeditioners is suggested. As fitness was lowest on arrival in Antarctica yet station workloads heaviest at this time, physical training prior to arrival in Antarctica is recommended for future expeditions.