The dielectric constants of GaAs, CdTe, and ZnSe and their temperature dependences were found from low‐frequency capacitance measurements. From 100 to 300 °K the dielectric constants vary linearly with temperature. No electric field dependence was found up to 104 V/cm, nor frequency dependence between 20 Hz and 1 MHz. The dielectric constants extrapolated linearly to 0 °K are 12.35±0.09, 10.31±0.08, and 8.80±0.07 for GaAs, CdTe, and ZnSe, respectively. The temperature coefficients λ (≡ϵ (0)−1 dϵ/dt) are 2.01×10−4/°K, 2.27×10−4/°K, and 1.71×10−4/°K, respectively, with an accuracy of ±0.02×10−4/°K.