The Vitatron has been used as designed by the manufacturer under routine laboratory conditions (Broughton, P.M.G., Buttolph, M.A., Gowenlock, A.H., Neill, D.W. and Sleutelberg, R.G. (1969) J. Clin. Pathol. 22, 278). We assessed the possibilities of the AKES with regard to determination of the activities of three enzymes: alanine transaminase (AIT), aspartate transaminase (AsT) and lactate dehydrogenase (LDH) in serum. Precision, accuracy, carry over and sample-diluent contamination were evaluated. This resulted in recommendations for optimal use in terms of capacity and precision, which were supported by computations on a mathematical model for measuring results.