Consumption of fermented sour milk (Rob) is a part of Sudanese culture. It is a common practice for the people in the rural areas of the middle and Western Sudan to prepare traditionally their Rob. In this investigation, the chemical, biochemical and microbiological aspects of Rob obtained from different sites in the Gezira province were studied. In addition, the fermenting microorganisms were isolated, purified and identified using different methods known for their high reliabilities. The quality of raw milk delivered from the same sites was also evaluated. The average chemical characteristics were 88.4 + 0.98% moisture, 0.70 + 0.05% ash, 3.1 + 0.14% protein, 3.02 + 0.75% fat, 11.48 + 0.17% total solids, 4.6 + 0.1% lactose, 8.46 + 0.2% solids-non fat, 0.16 + 0.02% titrable acidity and a pH of 6.5 + 0.13. Rob was made at the laboratory using pasteurized milk in the Department of Dairy Technology, College of Agriculture, of Gent University, Belgium, where some of the experiments were conducted. The product had a noticeable reduction in the characteristic buttery flavour of traditional Rob, and it has the following chemical composition: 4.2% protein, 0.34% fat, 0.84% ash, 7.8% total