Morel’s (or abscess) disease is a non-fatal, contagious disease of sheep and goats caused by Staphylococcus aureus anaerobius. The disease is endemic in nature with high morbidity rate and frequent relapses. In 1990s, this disease caused rejection of many shipments of Sudan's exported sheep with estimated losses of some millions US dollars. This initiated a research project to study the disease and to produce a protective vaccine: the outcome was the production of a vaccine with more than 96% protection. The present work represents a continuation of previous studies on this disease in the Sudan and elucidates some of the efforts done in this respect. Immunity conferred by Morel’s disease vaccine in sheep was assessed and monitored by plaque forming cell assay and opsonphagocytosis, protective dose of the vaccine was evaluated and determined, molecular techniques were used to investigate for genetic differences between local and reference strains of S. aureus anaerobius, some staphylococci isolated from lymph nodes abscesses of slaughtered sheep were tested for ability to cause clinical abscess disease. The main part of this work was carried out at the University of Khartoum, Sudan.