Background: There is a lack of appropriately designed trials investigating the efficacy of psychosocial interventions for patients with mild dementia and their family caregivers. This paper reports the rationale and design of the Danish Alzheimer Disease Intervention Study and baseline characteristics of the cohort. Methods: The study was a 1-year multicentre randomized controlled rater-blinded trial with randomization to follow-up and a multifaceted semitailored intervention programme or to follow-up only (with extension of follow-up to 3 years). The intervention included a counselling programme, teaching courses, written information and logbooks. The outcomes included clinical efficacy parameters, patient satisfaction and health economic consequences. Results: A total of 330 patients and their 330 caregivers were included during a period of 18 months. The majority (65.2 %) of the caregivers were spouses. At inclusion the mean age of the patients and caregivers was 76.2 and 66.0 years, respectively. Conclusion: The study will explore the added value of a multifaceted intervention programme and contribute to the design of future interventions for patients with mild dementia and their caregivers.