OBJECTIVES:   Blood pressure (BP) values in response to antihypertensive treatment are influenced by both physician- and patient-level factors. We quantified summary estimates of variability in BP values attributable to a physician-level class effect across six observational studies. METHODS:   We evaluated 90-day BP data on 14,116 patients, in whom prior treatment failed or was not tolerated, who received valsartan-based therapy for the treatment of hypertension. Data were collected during six consecutive prospective, observational, multi-center, pharmaco-epidemiologic studies conducted in Belgium between 2005 and 2009. Each study was designed to collect data from patients and their treating physicians. We applied a two-level hierarchical linear modeling method, using mixed-effects regression with residual maximum likelihood estimation. From these data, intraclass correlation coefficients (ICC)s were calculated to quantify the variability in 90-day systolic BP (SBP) and diastolic BP (DBP) values attributable to within-physician variability in each study. We then completed a random-effects meta-analysis of ICC point estimates and variance from each study, to account for within- and between-study differences, and derived ICC summary estimates and 95% confidence intervals (CI). RESULTS:   Summary estimates of absolute reduction in 90-day SBP and DBP across studies were -18.17mmHg (95%CI= -16.84 to -19.51mmHg) and -9.73mmHg (95%CI= -9.22 to -10.24mmHg) respectively. ICCs for SBP ranged from .210 to .277, with a random-effects summary estimate of .238 (95%CI= .220 to .256; p<.0001; τ=.002; I2<1%). ICCs for DBP ranged from .176 to .282, with a random-effects summary estimate of .255 (95%CI= .229 to .282; p<.0001; τ=.022; I2=45.69%). CONCLUSIONS:   Considering within- and between-study differences in ICC, the average proportion of variance in 90-day SBP and DBP values attributable to a physician-level class effect was between 22.0% and 25.6%, and 22.9% and 28.2% respectively. Further research is warranted to identify specific and amenable physician-level factors that contribute to higher BP values in response to antihypertensive treatment.