['To analyse the differences in ascitic and serum levels of immunoglobulins and albumin between two groups of cirrhotic patients (with ascitic total protein levels higher and lower than 10 g/l).', 'A prospective study.', 'We studied 39 cirrhotic patients with sterile ascites. The patients were classified into two groups: group A (18 patients) comprised those with an ascitic total protein level less than 10 g/l and group B (21 patients) those with an ascitic total protein level higher than 10 g/l. Ascitic and serum levels of albumin and immunoglobins G, A and M were analysed.', 'Ascitic immunoglobulin G and A levels in group B were higher than ascitic immunoglobulin G and A levels in group A. Ascitic levels of these immunoglobulins correlated linearly with ascitic total protein levels. The serum levels of immunoglobulins G and A in groups A and B were not significantly different. Ascitic and serum immunoglobulin M concentrations in the two groups were similar. Transfer of immunoglobulins G and A and albumin from plasma to ascites seemed to be similar in group B. Transfer of immunoglobulins G and A seemed to be impaired in group A. Differences in ascitic immunoglobulin levels between groups A and B were also observed in the presence of diuretic treatment. Differences in ascitic immunoglobulin levels were related to the Child-Pugh score.'] Is low protein concentration in cirrhotic ascites related to low ascitic concentrations of immunoglobulins G and A?