The response of groundnut to different amounts of irrigation water and the effect of irrigation on the occurrence of chlorosis during the establishment period of the crop were studied in south-west Cyprus in 1984–88. The irrigation requirement of groundnut for the entire growing season was found to be 480 mm. Under-irrigation resulted in a soil water deficit and reduced production. Application of water in excess of requirement also reduced yield. Daily evapotranspiration under optimum soil moisture conditions increased from 1·5–2·0 mm at the beginning of the growing season to 7·0–7·5 mm at full crop development; it then decreased to 2·0–3·0 mm by the end of the season. In soils of low CaCO3 content, neither frequent water application nor over-irrigation during the crop establishment period caused any chlorotic symptoms or affected yield.