In order to assess the systemic toxicity of Zwittergent 3-14, a detergent used in the protein-detergent complex vaccines for its attractive immunogenic properties, a subacute toxicity study was performed. In this 4-week toxicity experiment five female and five male rats per group were injected intramuscularly with 0.25 ml of 0, 75, 750 and 7500 micrograms Zwittergent ml-1 sterile saline solution. Body weight and food intake were recorded weekly. At day 24 urine was collected for semiquantitative (pH, protein, ketone bodies, bilirubin and occult blood) and quantitative analyses (protein, creatinine and volume). At the end of the experiment blood was sampled for haematological [haemoglobin (Hb), packed cell volume (PCV), erythrocytes, leucocytes, reticulocytes and thrombocytes and differential white blood cell count] and biochemical analyses (alanine aminotransferase and aspartate aminotransferase. At necropsy brain, heart, liver, kidneys, spleen, thymus, adrenal glands, thyroid, pituitary gland, uterus, ovaries and testes were weighed. The underlined organs and the musculus quadriceps including the injection sites were examined histopathologically. Indications for systemic toxicity were noticed in the high-dose group and included occult blood in urine, elevated protein/creatinine ratio concomitantly with an increased urine volume and increased relative kidney weight indicating a slight disturbance of the kidney function. Some changes in haematological parameters (decreased PCV and increased numbers of thrombocytes eosinophils and monocytes) and a decreased glycogen content in the liver were recorded in the high dose group. These changes may be secondary to the extensive inflammatory reaction observed in the muscle of this high-dose group.(ABSTRACT TRUNCATED AT 250 WORDS)