Medical treatment of juvenile idiopathic arthritis (JIA) has advanced in the last decade, and improved prognosis is a reality in daily clinical practice. Despite this improvement in the quality of treatment, the outcome can still be compromised by modifiable factors, including delayed referral to a specialist, delayed drug treatment, poor adherence to treatment, and early interruption of drug treatment. In this review we discuss the most relevant aspects related to adherence to treatment in JIA, with emphasis on: factors that affect adherence to treatment; effect of poor adherence to treatment on JIA prognosis; when to suspect and how to assess poor adherence to treatment; and strategies to promote adherence to treatment, with an emphasis on information-reinforcement education. Besides presenting the findings of other authors, we also try to report our experience of this subject, which is still a challenge for health professionals.