In this study, microwave assisted transesterification of waste frying oil was carried out in the presence of sodium methoxide (NaOCH3). Parametric studies were performed to investigate suitable reaction conditions such as catalyst amount (0.5-0.75-1.0-1.5 wt.%), reaction time (3-5-7-9 mm), temperature (55-60-65 degrees C), and oil:methanol ratio (1:4-1:5-1:6). Methyl ester content of biodiesel was determined as 90.04-98.85%. Methyl ester content of biodiesel was increased from 90.04% to 97.74% by molecular distillation at 170-200 degrees C, 10 mbar and 0.12-0.24 mL/min feed flow rate. Optimum distillation conditions were determined as 0.18 mL/min feed flow rate and 170 degrees C evaporator temperature by using 4 x 3 factorial design. (C) 2012 Elsevier Ltd. All rights reserved.