The outcome of surgical palliation was evaluated in 26 children with complex cyanotic congenital heart disease. Outcome was examined in terms of ongoing symptoms, exercise tolerance, and the ability to participate in normal childhood activities. An activity score was calculated and each child performed graded treadmill exercise testing. Breathlessness (24 (92%) children), respiratory infections (nine (35%) children), and leg cramps (eight 31%) children) were the most common physical disorders. Although formal exercise testing showed a clear reduction in exercise tolerance compared with age and sex matched controls, palliation had allowed 23 (89%) to function with moderate exercise limitation, three (11%) having severely limited activity. Parents underestimated the child's exercise tolerance in 80% of cases. Sixteen (62%) patients attended school full time, eight (31%) attended part time, and two (8%) received only home tuition. Palliative surgery can give children with a single functional ventricle a level of activity which allows them to take part in most childhood activities. Subjective estimates of exercise tolerance are inaccurate in this group of children, and formal exercise testing can contribute useful information to decision making about further surgical intervention.