Anaemia is a very common condition during pregnancy. This is particularly so in developing countries where the level of intake of iron rich foods is low; malaria and other intestinal parasites are common. This study was conducted to determine the prevalence of anaemia and the type of anaemia existing in pregnant women in Morogoro municipality. The effect of anaemia on infant birth weight was also examined. Twenty randomly selected pregnant women in their last trimester of pregnancy were studied. The subjects were recruited from the three maternal and child health clinics in the municipality. The subjects were not taking iron, folate or vitamin B12 supplements at the time of the study. Blood samples were collected from subjects during their routine visit to maternal and child health clinics. A series of determinations was conducted to determine haemoglobin concentration (Hb); packed cell volume (PCV); red blood cells count (RBC); serum iron (SI); and total iron binding capacity (TIBC). The effect of anaemia on the weight of new born babies was examined by calculating the correlation coefficient of birth weight and haematological indexes. The mean values (SD) of haematological indexes were as follows: Hb 8.7 +/- 1.5 g/dl; PCV 30.4 +/- 5.1%; RBC 2.5 +/- 0.6 x 10(2)/l; mean corpuscular haemoglobin concentration (MCHC) 28.9 +/- 4 g/dl; mean corpuscular volume (MCV) 151.5 +/- 120 fl and mean corpuscular haemoglobin (MCH) 35.2 +/- 7.9 pg. The results have shown that 95% of the subjects were anaemic at the time of the study. All subjects were suffering from iron, folate and vitamin B 12 deficiencies. This suggests that all subjects had a combination of microcytic and megaloblastic anaemia. The results have also shown that there was a positive correlation (r = 0.76; P = 0.01) between Hb concentration and weight of the infants at birth. Subjects who had Hb concentration of below 7.4 g/dl delivered infants that were weighing below 2500 g (mean birth weight of 2160 +/- 228 g). For those who had an Hb concentration of above 9.5 g/dl delivered infants weighing more than 3000 g (mean 3142 +/- 329 g). The mean birth weight of the infants born to anaemic subjects (Hb < 7.9 g/dl) was significantly lower compared to that of infants born to non-anaemic subjects. This observation suggests that anaemia had a significant influence on the birth weight of the infant. This could also be an indication of poor food security in general. Major causes of anaemia were identified as being poor dietary intake of iron rich foods and probably poor utilisation due to diseases such as malaria. All women had basic knowledge on anaemia. Most of the information was obtained from maternal and child health clinics (76%), schools (15%) and radio programmes (4%). However, despite their awareness on anaemia, the women were still anaemic. The main reason was lack of economic access to appropriate foods.