Objective. This paper assesses the quality of the underlying cause of death (COD) statistics in Hermosillo, Mexico in a random sample of 300 in-hospital adult deaths. Material and Methods. A "gold standard" COD, determined by a systematic review of hospital medical charts, was compared to the COD reported by the vital registry system. Results. Overall agreement between the reviewer and original COD at the ICD-10 chapter block was 69.2%, with a weighted kappa of 0.62. Agreement varied greatly by ICD-10 chapter. Mutual misclassification among common co-morbidities, such as diabetes mellitus and circulatory disease, minimized the net change in the mortality fraction assigned to each ICD-10 chapter after physician review. Conclusions. The ICD-10 chapter level underlying COD codes can be used to estimate disease burden in the population. Caution is recommended for use of vital registry statistics in Hermosillo for individual level or disease-specific analyses.