Canine lymphoid leukaemia is a relatively common lymphoproliferative disease in dogs. A definitive diagnosis and classification based on degree of cell maturation is crucial to stablish appropriate therapy and providing an accurate prognosis. Chronic lymphocytic leukaemia (CLL) has a very reasonable prognosis with survivals ranging from 1-3 years with minimal therapy while acute lymphoblastic leukaemia (ALL) has short lived responses to multiagent chemotherapeutic protocols, with survivals of barely 3-5 months. The diagnostic process is much more straightforward these days as after an initial haematology and blood smear evaluation, flow cytometry often allows diagnosis in peripheral blood if high circulating numbers of neoplastic cells are present. This technique aids in differentiating acute from chronic leukaemia and even provides prognostic information for CLL as B cell types have shorter survivals as well as those dogs with leukemic immunophenotypic aberrant profiles. This webinar is provided by BSAVA Education Partner IDEXX. A collection of IDEXX ‘topic of the month’ webinars is available here.