Experiments on the nucleation rate and the crystal growth rate of caprolactam in a specially adapted to this purpose apparatus for melt crystallization in suspension are presented. Hydrodynamics experiments have demonstrated that it is possible to use the apparatus as a MSMPR crystallizer. The assumption that the linear crystal growth rate does not depend on the crystals size in the investigated system: caprolactam-0.78 wt.% water has been proved. The effect of the linear crystal growth rate, the suspension density and the specific power input on the secondary nucleation has been determined.