Relapses of Crohn's disease appear to be almost random. If these attacks could be reliably predicted, it might be possible to abort them with early treatment. In order to identify laboratory and clinical parameters that would predict an acute relapse, patients who had been assessed clinically in the three months prior to an attack were studied. Published clinical indices as well as variety of laboratory parameters were measured. The clinical indices and the serum C-reactive protein, orosomucoid, alpha 1-antitrypsin, and iron were increased at the time of the attack as compared to three months earlier, while only the clinical indices, orosomucoid and alpha 1-antitrypsin increased between three months and one month prior to the attack. There was a poor correlation of the parameters to each other. Further prospective studies are needed to determine the specificity of the suggested indices in predicting acute relapses of Crohn's disease.