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The aim of the experiment was to examine how wheat responded to extended period of high temperatures under controlled conditions to supplement field studies with these varieties on Lombok Island. Two Indonesian wheat varieties (Nias and Dewata) and two Australian varieties (Axe and Gladius) were examined in growth room experiments at 3 different temperature regimes 32/23°C, 28/20°C and 25/15°C day/night with 12 h daylight. Temperature and photoperiod were selected to simulate conditions on Lombok Island, at lowland (32/23°C) and highland (28/20°C) sites. A third temperature (25/15°C) was selected to represent temperature in a more temperate wheat producing area. The rate of plant development increases with high temperatures up to an optimum temperatures and slower after further increases. Despite being exposed to high temperatures from establishment, the effect of high temperature was more severe during the reproductive stage as seen by the fact that yield was more affected than dry matter accumulation and yield was most strongly related to grain number. Genetic variability in response to heat stress was evident with the Indonesian varieties being more tolerant to high temperatures than Australian varieties. Nias and Dewata produced higher yield and biomass.