The aim of the study was to investigate the hyaluronic acid concentration in middle ear fluid of patients with cleft palate as an indicator of the severity of the disease. Hyaluronic acid was examined in the middle ear fluid of 65 children (48 boys and 17 girls) subjected to cleft lip surgery in neonatal period up to 10 days of age. Patients were divided into 3 groups according to the course of the disease. First group consists of 15 patients with favorable course, second group consist of 25 patients with moderate course, third group included 25 patients with an adverse course. Hyaluronic acid levels were determined by commercially available immunoassay. The concentrations of hyaluronic acid in the middle ear fluid were as follows (mean+SEM): favorable course: 14253+2393 µg/l, moderate course: 7503+1345 µg/l, adverse course: 5905+2393 µg/l. Patients with adverse course and moderate course had significantly decreased hyaluronic acid levels in middle ear fluid compared to the patients with favorable course (P=0.02 and P=0.0018). Hyaluronic acid concentration is related to the course of the disease and the lowest values are most frequent in patients with an adverse course.