The last few years have seen much progress in our understanding of, and treatments for, eosinophilic leukaemia. In preparing this review, we used Pubmed and the archives of well-known Haematology journals to search for relevant research papers and reviews published in the last 5-10 years. In this article, we review the differential diagnosis and sub-classification of eosinophilic leukaemia, and go on to discuss clinical features, investigation and treatment of these disorders. We are increasingly able to classify clonal eosinophilias based on the underlying molecular genetic abnormalities, and prognosticate and treat patients according to this. The successful treatment of certain of these patients with imatinib, followed by a greater understanding of the mechanism of this treatment, has revolutionized the outlook for many patients with eosinophilic leukaemia. New similar tyrosine kinase inhibitors and other promising therapies are on the horizon.