ObjectivesThe primary objective was to estimate the proportion of non-adherence to antihypertensive drugs in patients with an apparently resistant hypertension despite optimal medical treatment. The secondary objective was to identify related factors to poor adherence. MethodsMonocentric, prospective and observational study, including consecutive patients, managed for an apparently resistant hypertension between January 2014 and December 2017, with an ambulatory blood pressure measurement (ABP) in the past year and a thorough etiological work up in the 2 past years. Hypertension was considered resistant if the daytime ABP was â„ 135/85mmHg and/or the 24hours ABPâ„to 130/80mmHg, despite 4 antihypertensive medications at optimal doses. Adherence to treatment was assessed by the eight-item Morisky Scale (MMAS-8). ResultsWe enrolled 386 patients, with a mean age of 64.6 years, and 48.2% of men. The mean office blood pressure, 24hours and daytime APB were 178.6/101.3mmHg, 164.4/97.2mmHg and 170.5/99.7mmHg respectively. The proportions of low, medium and high adherence were 24.5%, 47.6% and 27.9% respectively. Associated-factors with poor adherence were female sex, low education level, celibacy, polypharmacy and lack of home self-blood pressure monitoring. ConclusionOver two out of three patients with an apparently resistant hypertension under optimal treatment were partially or fully nonadherent to treatment in our study. Assessment of adherence would be systematic in these patients before implementing complex investigations or non-pharmacologic invasive procedures.