The characteristics of wastewaters from a fertilizer factory, producing NH 3, urea, diammonium phosphate (DAP) and nitrogen-phosphorus-potassium (N-P-K) fertilizer blends, were monitored in stages for 18 months to correspond with the various stages of production of the different fertilizer minerals. Analysis of physico-chemical parameters of the various wastewater categories gave the following results: temperature, 28·0–32·5°C; pH, 5·0–9·48; conductivity, 2·5–2900·0 μmhos/cm; turbidity, 2·8–17·0 NTU; colour, 5–45 platinum cobalt units; DO, 1·4–7·0 mg/l; BOD 5, 1·0–41·4 mg/l; TS, 1000–8640 mg/l; TDS, 800–7600 mg/l; TSS, 200–3480 mg/l; acidity, 3·0–1000·0 mgCaCO 3/l; alkalinity, 10–460 mgCaCO 3/l; chloride, 249–1779 mg/l; total hardness, 0·0–20·0 mgCaCO 3/l; salinity, 0·0–3·5‰; calcium, 0·0–18·0 mg/l; magnesium, 0·0–0·972 mg/l; potassium, 18·0–50·0 mg/l; sulphate, 0·0–6640 mg/l; orthophosphate, 5·0–64·0 mg/l; NO 3-N, 0·04–1·57 mg/l; NO 2-N, 0·0–0·09 μg/l; NH 3-N, 0·0–0·72 mg/l. Variable results were obtained for the total coliform and faecal coliform counts with a range from 0 to > 1100 MPN/100 ml. Culturable aerobic heterotrophic bacteria populations ranged from 0·53 to 3100 × 10 3 cfu/ml. The fluctuations in these parameters were attributed to seasonal variations, varying effluent volumes, due to increased production capacity of the fertilizer plant, and the type of fertilizer mineral produced. A review of the waste-treatment system in the fertilizer factory is suggested, in order to minimize the impact of the pollutant components of the effluents on the ecology of the receiving creek.