Abstract Plants of Lupinus albus were grown in controlled-environment rooms at 18°c day and 13°c night temperatures. During one of 3 growth stages between main stem floral initiation and the end of first order lateral flowering, plants were moved to another room at 28°c day and 20° c night temperatures. At each growth stage some plants were given adequate water while others were restricted. At the end of each treatment, plants were returned to the low temperature and received adequate watering. High temperatures depressed the weight of vegetative parts when applied before flowering but had no significant effect during subsequent growth periods, although growth and development rates were increased. Weight of vegetative parts was depressed by water stress but, except for the preflowering treatments, reproductive growth rate was increased by stress during the growing period. Final seed yield, however, was depressed by water stress and by high temperatures during the preflowering and main stem flowering periods even in well watered plants.