A CWCI analysis that provides background information along with detailed data and graphics on cumulative trauma (CT) claims in the California workers’ compensation system. CT claims are physical or mental injuries that arise over time from repetitive stress, motion, or exposures, rather than from a specific event or accident. The study identifies characteristics that differentiate CT claims from non-CT claims, and finds a strong association between attorney involvement and regional variation in the Los Angeles Basin and the high cost of CT claims.