The CMS National Plan and Provider Enumeration System currently lists 79 Research Study Specialist providers with a primary practice address in California, all registered under the Specialist NUCC taxonomy branch. Each clinician on this roster selected Research Study Specialist as their primary taxonomy at NPI enrollment — a self-reported classification that is updated whenever the provider files a correction with CMS. The count excludes organizations (group practices, hospitals, clinics operate under separate NPIs) and excludes providers who chose a different primary specialty even if they practice Research Study Specialist part-time.

At 79 enrolled providers, Research Study Specialist in California is a limited-supply market — that matters for search-radius decisions, because patients in California outside the largest metros often need to broaden to adjacent cities to find a local Research Study Specialist clinician. The directory below is paginated 50 providers at a time (2 pages total) and is sorted alphabetically by last name, so scanning for a specific practice usually goes faster than scrolling; on the provider detail page you'll find the full NPPES record including address, phone, credentials, and any published Medicare Part D prescribing activity for 2023.

Before contacting anyone on this list, verify the practice is still at the address shown — NPPES refreshes monthly, but providers who have relocated, retired, or changed employers may not have filed an NPI update yet. Important: PlainDoctor is a directory of publicly available CMS government data covering Research Study Specialist providers in California, not a quality ranking, a board-certification verifier, or medical advice. Always confirm credentials through the NPPES NPI Registry, the California medical board, and — where relevant — the ABMS, AOA, or the specialty's primary certifying body before making any clinical decision. Nothing on this page substitutes for a conversation with a licensed clinician.