Does anyone out there use 3H.thymidine for T cell proliferation assays? If so can you share your experience with 3H.thymidine from Perkin Elmer. We have batches that hydrolyse gradually but are still usable for up to a year and others that are useless within a few weeks. Does anyone know of an alternative company that can supply a reliable product? In the old days you could buy 3H.thymidine from Amersham that was totally stable so why can't PE produce a reliable product and, more importantly, why does the company not care to correct this for their customers?