We compared the diagnostic sensitivities of serum amylase, lipase (assayed enzymatically and immunologically), trypsinogen and elastase-1, the 2-h-timed urine amylase excretion and the ratio of amylase and creatinine clearances in the recognition of acute pancreatitis. Serial serum and urine findings from 39 patients with acute pancreatitis, and from 42 patients with non-pancreatic causes of abdominal pain (controls), as well as findings from 24 healthy subjects (normals) were studied. Decision thresholds were established for each parameter using either the control or the normal population, and the resulting diagnostic sensitivities determined. On hospital admission, all serum assays were equally sensitive, but on subsequent days lipase, trypsinogen and elastase-1 assays all significantly surpassed the sensitivity of the serum amylase assay. On the second and subsequent hospitalization days, determination of timed urine amylase excretion offered no advantage over the serum amylase, and the ratio of amylase and creatinine clearances lacked discrimination altogether.