Plasma gastrin immunoreactivity was measured by radioimmunoassay in 45 dogs with acute gastric dilatation-volvulus (GDV). Significant increases (P less than 0.05) were found in dogs with acute GDV and in the fasted state after surgical treatment and recovery. The data suggested that dogs that have had GDV may have preexisting high plasma gastrin immunoreactivity. In dogs with acute GDV, plasma gastrin immunoreactivity was not found to be helpful in formulating prognosis. Circumcostal gastropexy did not affect plasma gastrin immunoreactivity.