PulMiCC (Pulmonary Metastasectomy in Colorectal Cancer) is a randomised controlled trial funded by Cancer Research UK. Patients with a history of resected colorectal cancer who are found to have pulmonary metastases are first registered for evaluation and, if subsequently eligible for the trial, they are invited to be randomly allocated to 'active monitoring' or 'active monitoring with pulmonary metastasectomy'. The clinical outcomes are overall survival, relapse-free survival, lung function and patient-reported quality of life.