Factorial combinations of two daylengths (11 and 12 h), two day temperatures (30°C from sowing to maturity or from sowing to day 90 and then 35°C to maturity) and warm and cool nights (8° and l0°C) were imposed on 15 chickpea cultivars grown in pots in an automatically-controlled glasshouse. All plants were inoculated with the same single strain of Rhizobium and vapour pressure deficits were maintained at much the same value in each environment by flooding the floor of the daytime compartments with water: Because cultivars differing in relative maturity (early, mid-late and late) were tested it was possible to quantify several responses to the aerial environments imposed. The group of cultivars suffered severely when plants matured in hot days, when average seed yield was reduced by about one-third. Some cultivars escaped stress during the reproductive period by maturing early; others were clearly adapted to specific environments whilst some can probably adapt to a wide range of conditions. It seems likely that many chickpea cultivars are sensitive to heat stress during reproductive growth. Comparisons are made with cultivars grown in the field in India and in growth cabinets at Reading and the implications of these data for chickpea crop improvement programmes are discussed.