Carnitine status was evaluated in 8 patients with partial ornithine transcarbamylase (OTC) deficiency and 19 patients with secondary carnitine deficiency, who were used as positive references. Laboratory findings indicated that all patients with OTC deficiency had secondary carnitine deficiency especially in hyperammonemic attack. After L-carnitine administration in 2 patients with OTC deficiency, the number of attacks was significantly reduced in both cases.