For the interpretation of the EPR lineshape of incommensurate phases there exist many theoretical models. We suppose a simple physical model to interpret the lineshape of the Mn 2 + EPR spectrum of the first incommensurate phase of betaine calcium chloride dihydrate (BCCD) and discuss it in comparison with other models. Furthermore, we investigate the critical behavior of BCCD at the normal to incommensurate phase transition on the basis of our model. The influence of the Mn 2 + impurities on the phase sequence of BCCD is investigated by dielectric measurements.