The methodology and preliminary results are presented of a census conducted in September 1991 in the Dogon country of the district of Sangha, Mali. Dogon country is located in eastern Mali and covers the length of the Bandiagara Cliff, around 200 km. 3 levels are distinguished topographically, the plateau, the cliff with altitudes ranging from 400 to 1000 m, and the plain. Each has a different style of living. The climate is Sahelian, and there are no important rivers to provide extra water. The study was done in the 56 villages of the district of Sangha which extends the length of the cliff. 40 were villages along the cliff and 15 were on the plateau at an average of 2-3 km from the cliff. The Dogon are the largest ethnic group in the region, but there are also Peuls at the foot of the cliffs. The Dogon are agricultural and the Peul are herders. The population census was the 1st stage of a general study of population genetics organized by the Department of Anthropology and Population Genetics of France's National Institute of Demographic Studies. The enumeration took place over 18 months from January 1990 to August 1991. Heads of households were interviewed and their official tax identification cards were reviewed. All persons including migrants and deceased persons who were mentioned by any respondent were included. Each person received a unique number composed of the number of the quarter of residence, the number of the family, and the number for the individual in the family. Married women do not immediately move to the husband's residence. Married women were counted where they actually resided at the time of the census. Methodological problems were encountered in defining families. The criterion of common residence was replaced by a locally more valid 1 of descent from a common ancestor, sharing of meals, and obedience to the same extended family head. Dating of ages was, as expected, difficult, but at this stage an internally coherent approximation was considered adequate. The duration of data collection was the most significant methodological problem but was unavoidable given the various constraints. The total Dogon population of the 56 villages was around 18,360 persons in 1421 families. Half the population (9243 persons) lived in 16 plateau villages. The average size of villages was 328 persons, but plateau villages contained 578 vs. 228 for cliff villages. Cliff villages had simpler family structures. 50.2% of a subsample of 8 of the villages were under 20 years old. Migration, temporary or permanent, has had a significant effect on the age and sex composition of the population.