Background. Patients may develop primary (congenital) or secondary (acquired) lymphedema, causing significant physical and psychosocial problems. To plan treatment for lymphedema and monitor a patient's progress, swelling, and problems in functioning associated with lymphedema development should be assessed at baseline and follow-up. Objective. The purpose of this study was to investigate the reliability (test-retest, internal consistency, and measurement variability) and validity (content and construct) of data obtained with the Lymphoedema Functioning, Disability and Health Questionnaire for Lower Limb Lymphoedema (Lymph-ICF-LL). Design. This was a multicenter, cross-sectional study. Methods. The Lymph-ICF-LL is a descriptive, evaluative tool containing 28 questions about impairments in function, activity limitations, and participation restrictions in patients with lower limb lymphedema. The questionnaire has 5 domains: physical function, mental function, general tasks/household activities, mobility activities, and life domains/social life. The reliability and validity of the Lymph-ICF-LL were examined in 30 participants with objective lower limb lymphedema. Results. Intraclass correlation coefficients for test-retest reliability ranged from.69 to.94, and Cronbach alpha coefficients for internal consistency ranged from.82 to.97. Measurement variability was acceptable (standard error of measurement=5.9-12.6). Content validity was good because all questions were understandable for 93% of participants, the scoring system (visual analog scale) was clear, and the questionnaire was comprehensive for 90% of participants. Construct validity was good. All hypotheses for assessing convergent validity and divergent validity were accepted. Limitations. The known-groups validity and responsiveness of the Dutch Lymph-ICF-LL and the cross-cultural validity of the English version of the Lymph-ICF-LL were not investigated. Conclusions. The Lymph-ICF-LL is a Dutch questionnaire with evidence of reliability and validity for assessing impairments in function, activity limitations, and participation restrictions in people with primary or secondary lower limb lymphedema. © 2014 American Physical Therapy Association.