Between 2002 and 2006, a large number of juvenile northern goshawks (Accipiter gentilis) with central nervous signs were examined. They were aged between 45 and 55 days and had been fed on frozen and thawed day-old chicks. High-performance liquid chromatography showed that the birds had whole blood thiamine levels between 2·2 and 6·0 μg/l; the concentrations of other blood constituents were within their reference ranges. Treatment with thiamine hydrochloride rapidly resolved the clinical signs. Measurements of the concentration of thiamine in 22 free-ranging and captive goshawks showed that they ranged from 45·1 to 200 μg/l.