Although current asthma guidelines stress the importance of assessing and enhancing adherence to asthma treatment, medication adherence rates in asthma patients are consistently low in practice. In this review, we summarize current literature on method of measurement, prevalence, outcome and intervention of medication adherence in asthma patients.Nonadherence to prescribed treatment continues to be a frequent problem in patients with asthma even in recent years. Objective measurement of adherence should be implemented whenever possible. Review of pharmacy refill data or electronic monitoring of inhaler actuation may be a preferred method to assess adherence. Educational programmes should be specifically designed to address the unmet need and specific reasons for nonadherence for the target population. Large, well designed clinical trials to assess the efficacy of remote electronic monitoring and reminder systems to improve adherence are needed.There is an urgent clinical need for systematic, proven methods to assess and address medication nonadherence in asthma patients.