This study was realized in the shrubland area of the Instituto de Ciencias Agrícolas (ICA) of the Universidad de Guanajuato, to determine the regression equation and dimensional variables that forecast with greater exactitude the aerial biomass of catclaw (Mimosa biuncifera), a shrub important for its density and the part it plays in the ecosystems where it is found. A random sample of 15 shrubs was taken in the stages of growth, flowering, maturity and latency, measuring the height, number of basel stems and their diameter; the greater and lesser diameter of the shrub top; and in determining the area and volume of the shrub. The biomass of the leaves plus the small branches and stems was obtained, culting the shrubs even with the soil. A multiple linear regression analysis was made. In the estimation of the biomass of leaves plus small branches the most important dimensional variable and the r2 value of the equation for growth, flowering and maturity was 0.7118, 0.8561 and 0.9507 respectively, while in latency it was the minor canopy diameter and r2 = 0.7117. For the estimation of dry weight of stems it was plant height and r2 =0.9104, the minor canopy diameter and r2 =0.8851, the number of stems and r2 =0.9728, and the minor canopy diameter and r2 =0.6275.