Estimated nutritive quality of forages in the San Carlos County, Costa Rica. II. Cell wall components. A total of one hundred and ninety two compound samples of Cynodon nlemfuensis, Setaria anceps, Brachiaria ruziziensis, Pennisetum clandestinum and Pennisetum purpureum was taken in commercial dairy farms in the Quesada district, San Carlos county. This area is located in the Humid Tropics of Costa Rica at 200 to 1 600 masl and samples were taken during a year period, to analyze fiber or cell wall components in order to generate information for improving dairy cattle feeding practices, as well as to obtain data required by summative equations to stimate energy content of forages. Setaria anceps, Brachiaria ruziziensis and Pennisetum clandestinum were sampled during the semidry and rainy seasons at26 to 30 days of regrowth. Meanwhile, Cynodon nlemfuensis was sampled at 20 to 25, and 26 to 30 days and Pennisetum purpureum at 50 to 60 days of regrowth. Cell wall composition was analyzed in terms of NDF, ADF, hemicellulose, cellulose, lignin, silica and neutral and acid detergents insoluble nitrogen. Average values found for these variables in grazing species were 69.5, 38.6,30.9,37.3, 5.04,2.87,0.82 and 0.27 per cent of DM, respectively. For Pennisetum purpureum values were 7 2.5, 51..5, 27.7, 38.6, 6.89, 5.38, 0.63, and 0.26 per cent of DM. Significant differences (P<0,05) were found among species and seasons for all variables analyzed. In general, all variables evaluated are within the typical range of well managed tropical Pastures. Results suggest that if forage availability and intake are adequate, all forages in the zone satisfy NDF and ADF requirements of dairy cattle. However, high NDF contents, such those observed in Cynodon nlemfuensis and Pennisetum purpureum, may limit voluntary intake.