Rationale: One in three patients experience depression after stroke and this risk is consistent over time. A strategy to prevent depression that could be economically delivered to most stroke patients and ideally which also has a low likelihood of adverse events needs to be developed and evaluated. Aims: POST aims to determine whether a simple intervention (postcards) prevents depression (Hospital Anxiety and Depression rating Scale, HADS depression subscale score ≥8) inpatients with a recent stroke. Secondary end-points include reduced anxiety (HADS anxiety subscale score ≥8) and improved health-related quality of life in patients with a recent stroke. Design: Asingle-centre randomised, double-blind, pilot trial to prevent depression in patients with a recent (within 8 weeks) stroke presenting to hospital. Patients will be enrolled over 12 months and randomised to receive three trial-specific assessments (baseline, 3- and 6-month assessments of mood, HRQoL and social functioning), or three trial-specific assessments plus a postcard sent centrally in a sealed envelope at 1, 2, 3, 4 and 5 months after discharge from hospital. Blinded follow-up telephone assessments will be conducted for both groups. Study outcomes and sample size: For the primary end-point the POST trial will have 80% power to detect a relative risk of 0.4 given an incidence of depression of 30%. For the secondary aims POST has 90% power to detect a difference of 3 points on the HADS depression subscale (assuming a standard deviation of 6 points) between randomised groups. This includes an inflation factor of 15% to account for patients lost to follow up. Discussion: Evidence of efficacy will determine whether a multi-centre, international trial is warranted.