ABSTRACT Objective: Few earthquake survivor studies extend follow-up beyond 2 years, leaving the long-term course of earthquake-related posttraumatic stress disorder (PTSD) unknown. This 10-year survey re-assessed the 1999 İzmit, Turkey, earthquake survivors. Methods: İzmit earthquake survivors (N = 198), previously assessed for PTSD/partial PTSD at 1–3 months and 18–20 months post-earthquake, were evaluated 10 years post-event from January 2009 through December 2010. A PTSD self-test (Turkish translation) used DSM-IV criteria to characterize full PTSD, “stringent partial PTSD,” “lenient partial PTSD,” or non-PTSD based on symptom type/amount. Results: Full PTSD prevalence decreased from 37% at 1–3 months post-earthquake to 15% at 18–20 months (P < .001), remaining relatively stable (12%) at 10 years (P = .38). Stringent and lenient partial PTSD decreased between 1–3 months and 18–20 months (from 9% to 3% and from 24% to 12%, respectively; P < .001), remaining stable at 10 years (5% an