A quality conrol assesssment laboratories of clinical analysis was performed in March 1989. Glucose, urea, bilirubin, and GOT were determined in a sample of the same control serum. Statistical evaluation of the results showed that the coefficient of variation (CV) of each parameter was much higher than the internationally accepted values. A further evaluation included an internal precision control and an interlaboratory control. Urea, glucose and cholesterol were determined in twenty samples of the same serum lot per month by each laboratory. About 61 percent had an acceptable CV for glucose, 74.4 percent for urea and 65,6 percent for cholesterol