A Baby-Friendly Hospital (BFH) focuses on the needs of newborns and empowers mothers to invest their own natural gifts in their childrens health. In practical terms, a baby-friendly hospital or maternity institution will encourage and help women to breast-feed their babies, applying each of the "Ten Steps to Successful Breasst-feeding" developed by UNICEF and the World Health Organization. Thailand is one of twelve countries selected to initiate and implement the Baby-Friendly Hospital Initiative (BFHI). Nationally, 37 hospitals have agreed to join the BFHIs first phase and, before the end of 1992, all will be implementing BFH activities. Royal Irrigation and Bamarajnaradoon Hospitals, both of which are located in Nontharburi and have adopted the "Ten Steps" approach, were studied on quasi-experimental and time series bases. Three health care providers from each hospital and a total of 251 mothers who delivered at these two hospitals were interviewed using structured questionnaires. The major objective was to determine BFHI effectiveness on maternal breast-feeding practices one month after programme implementation compared to before programme initiation. Attention was also given to those steps which the hospitals could and could not practically implement as well as the identification of maternal factors which influence adherence to exclusive breast-feeding on discharge from each hospital. Results indicate that Royal Irrigation Hospital has implemented eight of the ten steps beginning from 17 February 1992. Steps three and five (i.e., inform all pregnant women about the benefits and management of breast-feeding as well as how to undertake and maintain the practice), however, have been carried out for some time. Bamarajnardoon Hospital has been implementing seven the ten steps for over two years. To be in line with instructions issued by the Ministry of Public Health, though, the hospital modified some of the steps. Free donation of milk samples to the hospital from milk companies and routinely, giving milk formula to newborns was stopped. Both hospitals are not yet fully able to follow step number 2 (to train all health care staff on breast-feeding) and step number 10 (foster the establishment of breast-feeding support groups and refer mothers to them on discharge from the hospital). Due to the BFHI, the prevalence of exclusive breast-feeding (defined as breast milk + water) on discharge from the hospital significantly increased in both hospitals. Specifically, the Royal Irrigation Hospitals rate increased from 1.9% before programme implementation to 92.6% afterwards. In Bamarajnardoon Hospital, this rate rose from 46.6% to 98.4%, respectively. Differences in mothers age, education and occupation do not significantly influence breast-feeding prevalence while mothers are still at the hospital. Mothers, who upon discharge from the hospital were breast-feeding, however, are 14 times more likely to maintain breast-feeding at home until their infants reached 1 to 4 months, than mothers who were discharged with other types of feeding regimens from the hospital. The study also clearly revealed that the modification of maternity care services in line with the BFHI played an important role in supporting the prevalence of breast-feeding on discharge from the hospital.