BackgroundFollowing the development of resistance to anti-malarial mono-therapies, malaria endemic countries in Africa now use artemisinin-based combination therapy (ACT) as recommended first-line treatment for uncomplicated malaria. Patients' adherence to ACT is an important factor to ensure treatment efficacy, as well as to reduce the likelihood of parasite resistance to these drugs. This study reports adherence to a specific ACT, artemether-lumefantrine (AL), under conditions of routine clinical practice in Kenya.MethodThe study was undertaken in Garissa and Bunyala districts among outpatients of five government health facilities. Patients treated with AL were visited at home four days after having been prescribed the drug. Respondents (patients ≥ 15 years and caregivers of patients < 15 years) were interviewed using a standardized questionnaire, AL blister packs were physically inspected and the adherence status of patients was then recorded. Multivariate logistic regression modelling was used to determine predictors of adherence.ResultsOf the 918 patients included in the study, 588 (64.1%) were 'probably adherent', 291 (31.7%) were 'definitely non-adherent' and 39 (4.2%) were 'probably non-adherent'. Six factors were found to be significant predictors of adherence: patient knowledge of the ACT dosing regimen (odds ratio (OR) = 1.76; 95% CI = 1.32-2.35), patient age (OR = 1.65; 95% CI = 1.02-1.85), respondent age (OR = 1.37; 95% CI = 1.10-2.48), whether a respondent had seen AL before (OR = 1.46; 95% CI = 1.08-1.98), whether a patient had reported dislikes to AL (OR = 0.62 95% CI = 0.47-0.82) and whether a respondent had waited more than 24 hours to seek treatment (OR = 0.73; 95% CI = 0.54-0.99).ConclusionOverall, adherence to AL was found to be low in both Garissa and Bunyala districts, with patient knowledge of the AL dosing regimen found to be the strongest predictor of adherence. Interventions aimed at increasing community awareness of the AL dosing regimen, use of child friendly formulations and improving health workers' prescribing practices are likely to ensure higher adherence to AL and eventual treatment success.