OBJECTIVES: In patients with hypertension, non-adherence to prescribed treatment may contribute to a significant increase in cardiovascular risk. The aims of this study were (1) to examine if two single-item physician-administered adherence scales are predictive of cardiovascular risk and (2) to evaluate whether adherence to antihypertensive medications is associated with at least a one percent reduction in cardiovascular risk over 90 days.  METHODS: Pooling data from seven observational studies, this analysis included 8,438 hypertensive patients taking valsartan. A ten-year cardiovascular risk (CVR) score was estimated following the risk scoring system proposed by the SCORE project in Europe. CVR score considered the following variables: age, total cholesterol, current smoking status, systolic blood pressure, and sex. At baseline and 90 days, physicians administered two single-item measures of adherence: the first item of the Basel Assessment of Adherence Scale (BAAS) and the Visual Analogue Scale (VAS). RESULTS: At 90 days, males (4,257) had a significantly higher CVR than females (4,091) (p<0.001). For BAAS-identified adherent patients, CVR decreased significantly by 2.6% from baseline to 90 days  (p-value<0.001). For BAAS-identified non-adherent patients, a significant but smaller decrease in CVR of 1.3% was observed (p<0.001). For VAS-identified adherent patients, CVR decreased significantly by 4.4% from baseline to 90 days  (p<0.001). However, a significant decrease of 4.3% (p<0.001) was also observed for VAS-identified non-adherent patients.  CONCLUSIONS: Patients identified as adherent using the first item of the BAAS showed significantly improved 10-year cardiovascular risk scores after 90 days of treatment with valsartan, compared to patients who were identified as non-adherent. The VAS scale was not sufficiently sensitive to determine the effect of adherence on cardiovascular risk score.