The FDA page at the link provided provides an overview of the 510(k) review process and timeline. It describes the acknowlegment procedure, Acceptance Review, Substantive Review, Interactive Review, AI Request and Decision Letter. It also provides a timeline and indicates all timeframes are in calendar days. Full Manual Link: http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/HowtoMarketYourDevice/PremarketSubmissions/PremarketNotification510k/ucm070201.htm