Dynamic activities of &agr;, &bgr;, and screw dislocations in a GaP crystal containing sulphur as the main impurity at a concentration of 7×1017cm−3are investigated as a function of stress and temperature by means of the etch pit technique. Generation of all types of dislocations from a surface scratch is found to be suppressed at temperatures higher than 500 °C and is interpreted in terms of dislocation locking due to impurities and/or impurity‐defect complexes as has been observed in GaAs and InP. &agr; dislocations move faster than &bgr; and screw dislocations and their velocities are expressed with the same type of empirical equation as a function of the stress and the temperature as those in other semiconductors. Roughly speaking, dislocations in GaP move at velocities lower than those in GaAs by about two orders of magnitude.