This is an evaluation of the methodology of blood pressure measurement in a high-risk obstetric clinic. Blood pressure values were obtained from 149 patients by the clinic staff and the research project coordinator. The project coordinator using the random-zero sphygmomanometer measured lower systolic and higher diastolic values. The diastolic and systolic values increased after 30 weeks of pregnancy up to term. Agreement among observers is low for diastolic blood pressure. The clinic staff measured about 50% of the values with a zero terminal digit as compared with only 14% by the project coordinator. The fourth Korotkoff sound can be recorded in 83% of the patients. The mean diastolic blood pressures obtained with the fourth sound are significantly higher than when the fifth sound is used. Recommendations are offered for blood pressure measuring during pregnancy, and it is strongly suggested that the same methodologic rigor be used as in any other medical procedure.