Information obtained from a variety of sources shows different rates of initiation and duration of breast feeding and different supplementation strategies. Among populations of developing countries, in general, the mothers resident in rural-areas are more likely to breast feed than those in urban areas; in addition the better off or more highly educated are less likely to breast feed. In contrast in the developed countries, the better educated and the higher social class mothers are more likely to breast feed. There is some evidence that delay in initiation of breast feeding, lack of professional support, conflicting advice from health professionals and the presence of free samples of artificial milk (whether or not given to the mother) can result in a mother failing to establish breast feeding. Additionally, mothers who smoke cigarettes are less likely to breast feed successfully. Whilst breast feeding is almost universal in a number of developing countries, many also commonly use complementary feeds. In some countries, particularly in Asia, it is still commonplace for a child not to be given the mother's colostrum, and therefore for the first breast feed to occur well after the first 24 h.