Anemia in pregnancy is common in Tanzania. Previous information on distribution of hemoglobin concentration in total populations is scarce. Standard measurement of hemoglobin concentration in consecutive first visit attenders at the antenatal care clinic in Moshi, 1991-1994, for a total of 1800, divided into three series of 600 each. Hemoglobin concentrations ranged from 41 to 146 g/l, mean 96.9 and s.d. 16.3. For international comparison, 74.5% were below 110 g/l and 7.0% below 70 g/l. The median was 97.0; other percentiles were 10th: 75.0, 90th: 116.0. The distribution did not change with mother's age, but in the years 1991 and 1994 there were more low hemoglobin values than in the intervening years. Low hemoglobin concentrations are prevalent among pregnant women in Moshi, Tanzania. Seven percent were found to have severe anemia, defined as a hemoglobin concentration below 70 g/l.