Muscle and plasma concentrations of free and acylated carnitine (short-chain acylcarnitine and long-chain acylcarnitine) were determined by employing an optimized radiochemical-enzymatic assay in 14 healthy volunteers and in 10 patients with oesophageal carcinoma prior to elective operation. No significant correlations between total carnitine and its subfractions in muscle and plasma were observed and no sex differences were apparent. The estimated total carnitine pool in the patients (75.0 +/- 27 mmol) was significantly reduced compared to controls (130 +/- 24.3 mmol). The reduction was still present when expressed per kg muscle tissue (3.5 +/- 1.0 mmol versus 4.5 +/- 0.7 mmol) in order to consider age related decreased muscle mass in the patients. The muscular ratio of acylcarnitines to free carnitine was higher in the patients (0.23 +/- 0.10) than in healthy subjects (0.15 +/- 0.07), whereas the corresponding plasma quotient in the patients (0.22 +/- 0.09) was lowered compared to controls (0.30 +/- 0.10), indicating that instead of glucose, oxidation of fatty acids can be maintained, resulting in a preservation of the glycogen stores and thus an energy-conserving metabolic adaptation as a response to prolonged energy deficit.