The fine defect structure (native microdefects and as-grown dislocations) of pure and doped InP crystals are considered. Some kinds of point defects are detected. They are connected with the technology of crystal growth and impurity concentration. It is shown that the type and concentration of doping impurity essentially change the as-grown dislocation density and influence the mobility of freshly generated dislocations. The mechanism of plastic deformation under the action of a concentrated load is related to dislocation mobility in the InP crystals and impurity type.