Single crystals of p-type and n-type aluminum antimonide (AlSb) have been grown by the Czochralski method. Purification of the available aluminum is necessary if substantial carrier mobilities are to be achieved. The optical absorption coefficient was determined in the spectral region from 0.55 to 2.0 μ, which includes part of the principal absorption band. In addition to the absorption edge at 0.8 μ, weak absorption bands are observed in p-type material at 0.95 and 1.65 μ. Results are given for the Hall coefficient and carrier mobility in p-type AlSb as a function of temperature. At 300 K, hole mobilities in excess of 400 sq cm per volt-sec have been measured. The activation energy of the p-type impurity is 0.028 ev, and the temperature dependence of the hole mobility is T^−2.2. Data on n-type material are inconclusive because of the high degree of compensation.