The spin echo line shapes of Rb87 and Br79.81 have been measured in undeformed and plastically deformed RbBr single crystals. Analysis of the line shape of the measured echoes shows that the quadrupolar part of the echoes is given by point defects in the case of undeformed crystals, whereas in deformed crystals this term is determined by dislocations. A quantitative evaluation of the width of the quadrupolar shape yields the mean dislocation density in the samples as a function of the shear stress acting during the deformation. It was found that the square root of the dislocation density is proportional to the shear stress.