Objective: Washington State's work-related asthma (WRA) surveillance program utilizes workers' compensation (WC) data as its primary data source and has spanned a 15-year time period. This study analyses trends for WRA claim incidence rates compared to all WC claim incidence rates. WRA claim incidence rates and WC costs are analyzed by industry. Methods: Potential WRA cases were identified through the WC system and through direct provider report and classified by industry, age, and year of illness onset. WRA claim rates by industry and year were calculated using total work hours reported by employers covered by the WC system. Claim costs for accepted claims were compared by industry and year. Results: WRA claim incidence rates decreased 8.9% (95% CI: -10.6, -7.2) annually for the time period 2002-2016. The decline in WRA claim incidence rate is slightly faster than the incidence rate for all WC claims which had its steepest decrease from 2007 to 2010 at an estimated annual 8.4% decrease (95% CI: -11.8, -5.0). WRA claim rates were highest for workers in Public Administration, Manufacturing, and the Agricultural, Forestry, Fishing and Hunting industries. Median claim costs for WRA did not change significantly by year (p = 0.2, range $595-$1442) and the distribution of WRA WC claim costs by industry were highest in Manufacturing (21.3%) and Construction (16.4%) industries. Conclusion: WRA claim incidence rates are declining in Washington State. The cause for the decline is unclear. Workers across all industries in Washington remain at risk for WRA.