With use of a large data base and a statistical model for diagnosis developed earlier, we have constructed the among-individual conditional distribution of the long-term mean diastolic blood pressure, md, of an individual, given the means of several measurements of systolic and diastolic blood pressure on the individual. Using this conditional distribution we provide tables and a simple algorithm for computation of the conditional probability that md for an individual exceeds a specified value (for example, 90 mmHg), given the measured values of systolic and diastolic pressure.