The least square procedure was used to estimate the importance of some environmental factors affecting reproductive rate and milk production of Sudanese indigenous cattle raised under range conditions. The least squares estimates of age at first calving, calving interval, service period, gestation period, number of services per conception average daily milk and lactation period were 66·7 months, 447·0, 153·3, 287·2 days, 1·25, 3·58 litres and 232·4 days respectively. The year, but not the season at calving had a significant effect on age at first calving. Lactation number, year and season at calving all had significant effects on calving interval and service period. However only the last mentioned factor had a significant effect on gestation period and number of services per conception. The sex of the calf also influenced the gestation period. Only lactation number had a significant effect on average daily milk yield. On the other hand, the year at calving had a significant effect on lactation period, but not lactation number or season at calving.