A mass nutrient survey of southern Florida surface waters was made in September 1970, during a period of generally high water, and again in March 1971, during a period of low water. Water samples were analyzed by automated chemical techniques for total ortho plus acid-hydrolyzable phosphorus (P-P04), ammonia nitrogen (NH3-N), nitrate nitrogen (N02-N), and nitrate nitrogen (N03-N). Phosphorus (P-P04) concentration averaged about 0.50 mg/l (milligram per liter) during the wet season; the average concentration was slightly higher during the dry season. At many sites sampled during the wet and dry seasons, less that 0.01 mg/l of phosphorus was found. At one site in Broward County near a point of sewage outfall, the concentration was 45 mg/l during the dry season. Ammonia was the most prevalent form of nitrogen detected. Concentrations of NH3-N ranged from less than 0.01 to 14 mg/l in the wet season and from less that 0.01 to 25 mg/l in the dry season. Throughout the study area, nitrite and nitrate concentrations were generally low in both wet and dry seasons. Nitrite ranged from less than 0.01 to 0.70 mg/l N02-N during the wet season and slightly lower in the dry season. Most nitrate concentrations were below 0.20 mg/l N03-N during the wet and dry seasons.