The effect of haemodialysis on peripheral blood lymphocyte levels of total carnitine (TC), free carnitine (FC) and acylcarnitine (AC), and on the ratio of AC to FC, is investigated in 20 healthy subjects (13 men and seven women) and 27 patients (10 men and 17 women) with chronic pyelonephritis. The mean predialysis peripheral lymphocyte levels of TC, FC and AC were not significantly different from those in the healthy controls (P > 0.05). However, after haemodialysis, peripheral lymphocyte levels of TC, FC and AC decreased significantly, compared with either predialysis (TC: 40%, FC: 37%, AC: 52%) or healthy controls (TC: 61%, FC: 63%, AC: 50%) (P < 0.01). Furthermore, after haemodialysis the AC/FC ratio was significantly higher, compared with either predialysis (41%) or healthy controls (38%) (P < 0.01).