This account of lumpy skin disease is based on observations made when the author was Veterinary Investigation Officer in charge of the Regional Laboratory of the Federal Department of Veterinary Research, Kaduna, Nigeria. In 1974 a virgin epizootic of lumpy skin disease occurred and the disease became widespread throughout the north of Nigeria. Diagnosis, which was the primary function of the investigation laboratories, was based on a clinical appraisal of the disease supported by histopathology. This led to a confident though not definitive diagnosis. Tissue- culture work was not possible at Kaduna but virus isolation in embryonated eggs was successful though the virus was subsequently lost on passage. Earlier this year the author was afforded the facility of an electron microscope at the Department of Agriculture’s (Northern Ireland) Veterinary Research Laboratories, Stormont. Paraffin wax blocks of material from the 1974 epizootic were processed for electronmicrography and very satisfactory7 micrographs of the virus obtained. The application of this technique to the diagnosis of lumpy skin disease has not been previously recorded. The introduction to this account has been extended considerably to cover the history' of the disease including its economic significance in an attempt to put in perspective its spread to west Africa. This is followed by the author’s observations on clinical signs, histopathology, electronmicrography and virus isolation. In each section personal observations have been compared with existing records. The results of this study are not very different from those recorded in other countries but an attempt has been made to clarify and emphasise the salient and constant features of the disease which aid in its rapid diagnosis.