It was the aim of this study to compare the concentrations of total (TC) and free L-carnitine (FC) in blood serum of different groups of lactating cows. The animals were allotted into three groups, a) control animals (N = 11), b) cows with abomasal displacement (AD) (N = 5) and c) cows with puerperal disorders (PD) (N = 5). TC and FC were measured with an radioenzymatic assay. Blood samples were collected from 5 to 0 d before parturition (a. p.) and from 0 to 28 d after parturition (p. p.). It was of interest to examine whether L-carnitine might be limiting under certain conditions of metabolic stress which are typical for high yielding lactating cows. Concentrations of TC and FC (mumoI/l) in control cows before and after parturition were 10,0* and 8,6* and 6,0-8,9 and 3,7-4,9, respectively. The corresponding TC and FC values for cows with AD were 19,6* and 8,9* and 10,5-20,7 and 4,8-6,9, respectively. Cows with PD showed TC and FC concentrations a. p. and p. p. of 15,7* and 9,2* and 10,3-13,0 and 4,8-6,3, h other puerperal disorders PD respectively (* only one value).