This paper presents a comparison between tabular methods of determining fire resistance and calculation methods for flexural members as given in BS 8110. It considers both simply supported and continuous one-way spanning slabs. It continues by considering the effects of variations in steel strength, concrete strength and the temperature profiles within the element on the calculation of fire endurance periods, and concludes that the largest effect is due to variations in the calculation of temperature profiles, a lesser effect due to variation in steel strength and a negligible effect due to concrete strength. The paper also demonstrates that for the cases analysed, the calculation method gives a lower fire endurance than the tabular data. The reasons for this are probably due to inherent characteristics of the standard fire test. The paper concludes by giving a simple method for the calculation of the fire endurance of simply supported one-way spanning slabs which takes account of the level of loading. NOTATION a Ast b c d Thermal diffusivity (mm2/s) Area of tensile reinforcement (mmZ/m run) Width of compression block (mm) Cover to reinforcement from the tension face (mm) Effective depth to the reinforcement centroid (mm) Concrete strength (N/mm 2) 245 Fire Safety