Since the discovery of ferroelectricity in rochelle salt using dielectric measurements [1], many materials have been reported to be ferroelectric i,n the past several decades [2-4]. Measurements on dielectric properties, hysteresis loop, thermal expansion and structure are mainly used for establishing ferroelectricity in solids. These properties go through abrupt changes at the curie temperature and the hysteresis loop transforms itself into a straight line or an ellipse characteristic of a lossy condenser (above the highest curie temperature). Semicarbazide hydrochloride (CO(NH2)NH2NH-HC1) is reported to be a ferroelectric with curie temperatures at 230, 19 and 21 ° C using dielectric measurements [5]. However, it has been shown that there is no structural change, particularly from 0 to 21°C [6, 7]. As the isotope effect plays an important role in the phase transition of most hydrogen-bonded ferroelectrics, we have extended our attempts to study the effect of deuteration on these properties of SEM-HC1. This letter reports the results of our measurements of dielectric constant (K) and loss (tan 6) of semicarbazide hydrochloride (SEMHC1) and its deuterated single crystals (SEM-DC1) when they are grown by the supersaturated solution method using double distilled water, or when they are grown in heavy water. The frequency range covered is 102 to 1 0 7 H z and the temperature region 1 8 0 to 65 ° C. Thermal expansion measurements have been taken in the temperature region 14 to 65 ° C. Incidentally, these measurements together with hysteresis loop and structural studies indicate that these crystals are not ferroelectric. Single crystals of semicarbazide hydrochloride were grown at 25°C by slow evaporation of supersaturated solution using double distilled water or heavy water. Crystals grown in the temperature region 25 to 27°C with a concentration of 10g material in 30ml solvent were found to be of high quality. SEM-DCI crystals were obtained by recrystallizing SEM-HC1 with D20 (99.4%, supplied by the heavy water division, B.A.R.C., Bombay, India). The crystals were found to be quite transparent and have approximate dimensions of 4 x 1 x 0.5 cm3; samples were prepared from these large crystals and had dimensions of 1.5 x 1.5 x 0.1cm 3 for dielectric measurements. Samples with suitable dimensions were prepared for thermal expansion measurements and hysteresis loop study. The quality of the crystals was checked by X-ray diffraction technique. The cell parameters obtained for SEM-HC1 were a -0.753 (1), b = 1.318 (2), c = 0.469 (1)nm and for SEM-