OBJECTIVE: To explore trends in documented sexual abuse/assault (SA) related episodes in California hospitals and emergency departments (ED), including the impact of a change in health care service reporting codification (from ICD-9-CM to ICD-10-CM) that more clearly defined SA in October 2015. DATA SOURCES: Hospital and ED data were drawn from Californias Office of Statewide Health Planning and Development (OSHPD). STUDY DESIGN: Descriptive and trend analyses of SA-related hospital and ED records (including patients demographic information) were conducted to determine whether changes in ICD codification had an impact on documented SA-related episodes. DATA COLLECTION: All SA-related episodes (ICD-9-CM codes 995.83, 995.53; ICD-10-CM codes T74.21-T74.22, T76.21-T76.22) in California hospitals and EDs for the last decade of available data (2008-2017) were analyzed (n = 20,215). PRINCIPAL FINDINGS: An abrupt increase in documented SA episodes in hospitals and EDs began in October 2015, when specific ICD10 codes for suspected cases of SA were created. Documented SA-related episodes doubled in 1 month (164 vs. 385 episodes in September 2015 and October 2015, respectively). More than half (58.2%) of all SA-related episodes documented in Oct 2015 were coded as suspicious. The number of documented SA-related episodes continued increasing to the end of the time series (December 2017). Overall, the annual number of documented SA-related episodes increased by over 700% in only 4 years (900 vs. 6441 in 2013 and 2017, respectively), suggesting high rates of prior under-reporting and the need to introduce the new codes. African Americans were disproportionally impacted; however, the highest increases in age-adjusted rates between the ICD-9-CM and the ICD-10 codification period were found among the White population (2.46 vs. 16.53 per 100,000 inhabitants). CONCLUSIONS: SA episodes in the clinical population have been underestimated for many decades. Identifying SA victims and measuring SA-related health care utilization is a real challenge that needs further investigation.