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The objectives of this study were to determine 1) spatial variability of steady-state ammonia concentration on the pen surface, 2) the effect of environmental factors on ammonia concentration, and 3) the nutrient composition and concentration of odorous compounds in manure from the pen surface of beef deep-bedded, monoslope facilities. Four pens (27.5 x 30.5 m) in two commercial beef deep-bedded, monoslope facilities were studied. In each pen, ammonia was collected in acid traps at 56 locations using 640 cm2 flux chambers. Moisture, pH, pack height, nutrient composition and concentration of odorous compounds were measured at each sample location. Ammonia samples were collected at 6-week intervals for 10 months, all other samples for 18 months. There was no consistent spatial pattern of ammonia concentration. Areas of high ammonia concentration resulted from recent urination of cattle. Ammonia concentration decreased rapidly after cattle were removed from pens, reaching an apparent baseline after 4 hours. Ammonia concentration increased as pack and ambient air temperature increased (P < 0.01) and was lower in the cold months compared to moderate and hot months (P < 0.01). Depth and pH of bedded pack were affected by seasonal changes but were poorly correlated to the ammonia concentration on the feedlot surface of monoslope facilities (R2 = 0.07). Concentration of total volatile fatty acids (VFA), straight-chain VFA, and branch-chain VFA in manure were highest in the cold and moderate months and lowest during the hot months. The concentration of aromatic compounds in the manure was not affected by season.