Several endocrine tumor markers are routinely used in the diagnosis and management of various cancers. The current assays, however, typically take several hours to perform, which precludes their use in the intraoperative management of patients. The majority of the endocrine tumor markers have a half-life in the circulation of less than 5 minutes. Thus, if a rapid assay was available, the concentration of the hormones during surgery or during localization procedures could be monitored. The primary indication for such assays would be in assessing the extent of residual tumor after surgery and in the localization of the tumors by selective venous or arterial sampling. In the past year, we have evaluated a commercial rapid assay for parathyroid hormone (PTH) on over 50 patients and found that it provides valuable information for the surgical management of patients with hyperparathyroidism. We have developed an algorithm for the kinetic analysis of PTH decay following the excision of any adenomas that produces fewer misclassifications compared to the cur-rent procedure for interpreting the data. We have also developed an automated version of the assay using magnetic beads, that is faster and has a superior error-to-noise ratio. We plan in the upcoming year to compare the results of the new assay with the current assay. Similarly, we have developed a rapid ACTH assay, using magnetic beads, that we will also evaluate for its clinical utility. We also have plans to develop rapid assays for calcitonin and gastrin.