Phytomass was determined for a tropical deciduous forest in Chamela, Jalisco, México. The mean canopy height was 6.9 m, and the total basal area was 25.6 m2 ha−1 (dbh > 3.0 cm). The estimated phytomass for this forest (85 Mg ha−1) is among the highest values for tropical dry forests with similar seasonal climates. A stepwise multiple regression analysis showed that phytomass can be predicted firstly by basal area (R2 = 0.88), then by wood specific gravity (R2 = 0.91), and finally by the inclusion of tree height in the regression (R2 = 0.92). Each new independent variable explained significant variance in the phytomass estimation.