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Waste frying oil as valueless material which is disposed to environment can be used as a promising feedstock to produce biodiesel. In this study, constructional lime was used as alkaline heterogeneous catalyst for biodiesel production from virgin and waste frying oil. After determining the best activation temperature for the catalyst (600°C), transesterification reactions were carried out at 65°C, MeOH to oil molar ratio of 12:1, and 1 wt% of activated constructional lime under vigorous mixing for 5 h. Yield of reactions for virgin and waste frying oil (2.17 % free fatty acid) and pretreated waste frying oil (0.918 % free fatty acid) were 87, 93.9, and 94 %, respectively. Transesterification of virgin frying oil and pretreated waste frying oil were done at 65°C, MeOH to oil molar ratio of 6:1, and 1 wt% of KOH as catalyst under vigorous mixing for 2 h, for comparison. Yield of the reaction was 98.6 and 95.1 %, respectively. Therefore, when constructional lime is used as catalyst pretreatment of waste oil is not necessary.