In order to study the effect of pressure on famotidine, 3-[[[2-[(aminoiminomethyl)amino]- 4-thiazolyl]methyl]tio]-N-(aminosulfonyl)propanimidamide, two polymorphs already known, A (m.p. = 169.4 °C), and B (m.p. = 161.8 °C) were submitted to pressures of 200, 400, 600, 800 and 1000 MPa. Thermophysical study of the behavior, as a function of the temperature, of the fresh and treated samples was carried out by differential scanning calorimetry in the temperature interval between 20 and 180 °C. © 2002 Elsevier Science B.V. All rights reserved.