Silva GC, Jiang L, Gutman R, et al. - This study was carried out to analyze trends in the Veterans Health Administration (VA) for 30-day mortality following hospitalization for heart failure (HF) and pneumonia using claims-based and clinical risk-adjustment models. The primary endpoint included 30-day, all-cause mortality. All models included age and Gender. Claims-based covariates enrolled 22 (30) comorbidities for HF (pneumonia). The mean (SD) age was 71.6 (11.4) years and 144 502 (98.4%) were men; among the 131 325 admissions for pneumonia, the mean (SD) age was 70.8 (12.3) years and 127 491 (97.1%) were men among the 146,924 HF admissions. The adjusting for clinical covariates attenuated declines in mortality rates distinguished using claims-based models among HF and pneumonia hospitalizations. Evaluations of temporal trends in 30-day mortality applying claims-based risk adjustment should be interpreted with caution.