In the present work the production of biodiesel using bitter almond oil (BAO) in a potassium hydroxide catalyzed transesterification reaction was investigated. The BAO was obtained from resources available in Iran and its physical and chemical properties including iodine value, acid value, density, kinematic viscosity, fatty acid composition and mean molecular weight were specified. The low acid value of BAO (0.24 mg KOH/g) indicated that the pretreatment of raw oil with acid was not required. The fatty acid content analysis confirmed that the contribution of unsaturated fatty acids in the BAO is high (84.7 wt.%). Effect of different parameters including methanol to oil molar ratio (3-11 mol/mol), potassium hydroxide concentration (0.1-1.7% w/w) and reaction temperature (30-70 degrees C) on the production of biodiesel were investigated. The results indicated that these parameters were important factors affecting the tranesterification reaction. The fuel properties of biodiesel including iodine value, acid value, density, kinematic viscosity, saponification value, cetane number, flash point, cloud point, pour point and distillation characteristics were measured. The properties were compared with those of petroleum diesel, EN 14214 and ASTM 6751 biodiesel standards and an acceptable agreement was observed. (C) 2011 Elsevier Ltd. All rights reserved.