The effects of a 13 week health related fitness programme on selected physiological variables were studied using a time series design. Data were collected every 6 weeks for 11 months, with 10 Down syndrome subjects aged 8 to 18 years acting as their own controls. Analyses of results revealed significant positive changes for all variables (p<.05). It was concluded that participation in physical activity may be beneficial for Down syndrome subjects, particularly as poor fitness levels have been closely associated with health risks such as cardiovascular disease. School based programmes could play a crucial role in such participation.