The variations of cell area and number inDrosophilawing compartments following heat‐shock at different developmental stages have been studied in two unrelated stocks. In spite of different sensitivity to heat‐shock treatment, similar trends of response are exhibited by the two strains. At developmental stages when mitotic activity occurs, a general decrease of compartment areas is observed after treatment. The effect on the wing area appears to be mainly determined by the decrease of cell number, however cell area seems to compensate for cell number variations in the posterior compartment. The posterior compartment appears to respond earlier, than the anterior, possibly due to the different growth rate of the two compartments. We suggest that the genes for wing area determine the growth strategy of the wing compartments through pleiotropic effects on the genes for cell area and the genes for cell number.