One hundred and seven sunflower selections were examined by gas-exchange techniques for variations in photorespiration and photosynthesis. Photorespiration was positively correlated (r = 0.73) with true photosynthesis and constituted 14.3% of true photosynthesis or 16.7% of apparent photosynthesis. Selections with differences in compensation point or in the sensitivity of photosynthesis to O2 or CO2 which would be useful for further studies were not found. Photorespiration would seem to be closely linked to photosynthesis.