Abstract: A decade ago our laboratory started a major transition towards using primary cells in support of drug discovery programs for autoimmune and inflammatory diseases. Donor to donor variability was a major concern at the outset. With now >25 primary cell assays developed and employed for SAR and HTS, sufficient data has been accumulated to conduct a meaningful analysis of these assays in high throughput pharmacology. Analysis results will be presented – including an answer to the title’s question - along with specific lessons and strategies gathered along the way to facilitate the use of these physiologically relevant assays.