Given increasing demand for emergency care, there is growing concern over the availability of emergency department (ED) and inpatient resources. Existing studies of ED bed supply are dated and often overlook hospital capacity beyond ED settings. We described recent statewide trends in the capacity of ED and inpatient hospital services from 2005 to 2014.Retrospective analysis.Using California hospital data, we examined the absolute and per admission changes in ED beds and inpatient beds in all hospitals from 2005 to 2014.Our sample consisted of all patients inpatient and outpatient) from 501 hospital facilities over 10-year period.We analysed linear trends in the total annual ED visits, ED beds, licensed and staffed inpatient hospital beds and bed types, ED beds per ED visit, and inpatient beds per admission (ED and non-ED).Between 2005 and 2014, ED visits increased from 9.8 million to 13.2 million (an increase of 35.0%, p<0.001). ED beds also increased (by 29.8%, p<0.001), with an average annual increase of 195.4 beds. Despite this growth, ED beds per visit decreased by 3.9%, from 6.0 ED beds per 10 000 ED visits in 2005 to 5.8 beds in 2014 (p=0.01). While overall admission numbers declined by 4.9% (p=0.06), inpatient medical/surgical beds per visit grew by 11.3%, from 11.6 medical/surgical beds per 1000 admissions in 2005 to 12.9 beds in 2014 (p<0.001). However, there were reductions in psychiatric and chemical dependency beds per admission, by -15.3% (p<0.001) and -22.4% (p=0.05), respectively.These trends suggest that, in its current state, inadequate supply of ED and specific inpatient beds cannot keep pace with growing patient demand for acute care. Analysis of ED and inpatient supply should capture dynamic variations in patient demand. Our novel 'beds pervisit' metric offers improvements over traditional supply measures.