Abstract Manganese has been studied as a new acceptor impurity in bulk InP. Large single crystals which possess the lowest hole concentrations yet reported, 3 × 10 14 cm −3, have been grown by the liquid encapsulated Czochralski pulling technique. This low carrier level is due to the low distribution coefficient for the electrically active manganese, k active = 4 × 10 −3 and the high activation energy, 0.30 eV. In comparison, the acceptor commonly used to produce p-type material in InP, Zn, has a distribution coefficient of ≈1.0 which makes it especially difficult to achieve the low hole concentrations necessary for certain device applications. Optical absorption and photoluminescence data are also reported.