Information from a large clinical database was used to construct time trends for the leading associates of mortality among dialysis patients. The changing strengths of association of those measures with mortal risk were also evaluated. Strength did not change in meaningful ways for serum albumin, creatinine, or anion gap concentrations. It declined for the urea reduction ratio (URR), however, as prevalent values of the URR increased. Irrational patterns of association between the URR and other measures suggested reevaluation of the urea kinetic method for prescribing and judging dialysis dose. Two premises on which the urea kinetic equations rest are not valid if the context for their use is clinical outcome instead of predicting blood urea nitrogen (BUN) concentration. Rigorous use of the Kt/V criterion for dialysis dose could lead to clinical judgment errors, particularly underdialysis for small or malnourished persons. Changes for prescribing dose and judging therapy are recommended.