The lungworm Angiostrongylus vasorum is one of the five main parasites affecting dogs in the UK. It can cause severe illness and even death in infected dogs. Over the last few years, there have been advances in the diagnosis and treatment of angiostrongylosis. There have also been media campaigns aimed at increasing the profession’s and the public’s awareness of the disease, and strong promotional campaigns from companies that market anthelmintics. However, there is confusion about how best to manage preventive therapy. This module provides answers to key questions about the biology, epidemiology, clinical impact, diagnosis and management of canine angiostrongylosis. It will enable veterinary professionals to discuss confidently the risks with clients and reach a fully informed decision about preventive therapy.