Two crystal forms of the new dihydropyridine derivative, methyl (E)-3-phenyl-2-propen-1-yl 1, 4-dihydro-2, 6-dimethyl-4-(3-nitrophenyl)pyridine-3, 5-dicarboxylate (FRC-8411), were obtained by recrystallization from methanol. These crystal forms were identified by using powder X-ray diffractometry, infrared spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry. By means of DSC, the melting points of forms I and II were found to be 140 and 121°C, respectively.Forms I and II, having a similar particle size distribution, were administered orally or intravenously to spontaneously hypertensive rats. In the case of oral administration, the hypotensive action of form I was milder than that of form II and tachycardia was not observed after administration of form I.