The objective of the present work was to study the lobus frontalis in postmortem human brains in order to obtain weight as well as superficial and deep cortex values of the lobus and its gyri and quantitative ratios among these values. Twelve brains obtained from right-handed subjects aged between 30 and 55 years having no visible macroscopic neurologic lesions were fixed in formaldehyde (5%) and processed using a method developed in our laboratory (Arch. Neurol., 46:307; 1989). Absolute and percent values, as well as weight/cortical surface ratios and correlations of the gyri of the lobus frontalis - regio orbitalis, cinguli, superior+medium, inferior and precentralis - were obtained. The cortical surface of the right gyrus cinguli is significantly larger than the contralateral one. The statistically lower weight/cortical surface ratio corresponds to the regio orbitalis and the higher one to the gyrus precentralis. The regio orbitalis supplies a higher percentage in cortical surface than in weight to its respective lobus frontalis; the opposite occurs with the gyrus precentralis. The right gyrus cinguli supplies a higher percentage in weight than in cortical surface than the left one. The Pearson coefficient of correlation between the values (absolute and percent) corresponding to weight and cortical surface between homologous gyri of both hemispheres are positive.The correlations between weight absolute as well as percent values and those of the respective cortical surface are positive, excellent and highly significant. The higher percentage of cases with right laterality corresponds to the gyrus cinguli and that with left laterality to the gyrus frontalis inferior. Modifications that could occur in brains from psychiatric and neurologic patients could alter some of these values and relationships, as for example in schizophrenia in which we found an inversion of the gyrus cinguli anterior laterality (<A HREF="#albanese95">ALBANSE et al., 1995</A>)