OBJECTIVES To investigate several comorbidity classifications as possible predictors of mortality, because the value of comorbidity as a prognostic factor is uncertain in patients older than 70 years of age and radical prostatectomy in patients older than 70 years is controversial. METHODS A total of 214 consecutive patients aged 70 years or older who underwent radical prostatectomy from December 1992 to December 2002 were stratified according to the Charlson score, American Society of Anesthesiologists physical status classification, New York Heart Association classification of cardiac insufficiency, classification of angina pectoris from the Canadian Cardiovascular Society, and age (70 to 72 versus 73 to 74 versus 75 years or older). The mean follow-up in the surviving patients was 5.1 years (range 1.3 to 12.5). A sample of 240 consecutive patients aged 67.0 to 69.9 years treated during the same period was used for comparison. The overall and comorbid mortality were the study endpoints. Mantel-Haenszel hazard ratios were calculated. Comparisons were made using the log-rank test. RESULTS Unlike for patients aged 67.0 to 69.9 years, for those 70 years old or older, only one of the investigated stratifications reached significance as a predictor of mortality. A New York Heart Association classification of 2+ versus 0 was significant for overall mortality (hazard ratio 5.8, P = 0.021) and comorbid mortality (hazard ratio 15.9, P = 0.046). CONCLUSIONS Comorbidity is of limited prognostic value in patients selected for radical prostatectomy and 70 years old or older.