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[EN]The adsorption isotherms of nitrogen at 77 K have been determined on two series of activated carbons and two samples of activated carbon fibres. The carbons were highly microporous and contained varying amounts of different forms of microporosity. Characterization of the carbons was undertaken using an alternative linear form of the BET equation and the results of the BET parameters obtained have been compared with those obtained from the usual classical linear form of the equation. The surface areas calculated from the two linear forms were similar while the C values were quite different. The C values obtained from the alternative linear form appeared to be more reasonable, being consistent with and related to the microporous character of these carbons. The alternative linear form gave BET plots which were more sensitive to deviations from linearity allowing the relative pressure range for the application of the BET equation to be determined without any ambiguity and more precisely. ; The authors thank DGICYT (Project PB90-0067) and FICYT for financial support. R. C. Bansal is grateful to the Ministerio de Educación y Ciencia, Government of Spain for a financial grant for his stay at the Instituto Nacional del Carb6n in Oviedo, Spain. J.C. de Sousa also thanks the Univ. Est. de Maringa and CNPq (Brazil) for a grant. ; Peer reviewed