BRAF and MEK inhibitors are not established treatments for non-V600 mutation-positive metastatic melanoma. We carried out a retrospective analysis of efficacy and safety in four patients with BRAF K601E and one patient with L597Q mutation-positive metastatic melanoma treated with the MEK inhibitor trametinib. Three patients achieved a RECIST partial response, including the patient with an L597Q mutation. Paired biopsies available in one of the five patients showed reduced phospho-ERK signalling and this corresponded to a metabolic response on 18F-fluorodeoxyglucose-PET scanning. Trametinib toxicity was manageable. Trametinib has antitumour activity in patients with BRAF K601E and L597Q mutation-positive metastatic melanoma.