P- and n-type GaAs single crystals with as low as available initial carrier concentrations were dynamically deformed by plastic bending up to high dislocation densities. The radii of curvature were of the order of 2x10-3 m. Measuring the Hall effect and conductivity before and after plastic deformation the influence of dislocations on the electrical properties was investigated. The contamination during deformation was controlled by specimens which remained undeformed while heated. Both the carrier concentration and their Hall mobility decreased after deformation, independent of the sign of bending. The results are discussed in terms of "dangling bond"-states introduced into the gap