This study was conducted to investigate the mothers` nutritional knowledge on weaning of 101 infants (8 for 4 mo, 44 for 5 mo, 45 for 6 mo, 4 for 7 mo) at a public health center of Incheon. Informations on the mothers` nutritional knowledge were obtained by questionnaires. In this survey 41.6% of infants were breast-feeding, 43.6% of them were bottle-feeding, and 14.9% of them were mixed feeding right after birth. The rate of breast-feeding right after birth was significantly higher in mothers of high school graduate than mothers of college/university graduate (p < 0.05). The infants of mothers graduated high school began to be weaned significantly earlier than the infants of mothers graduated college/university (p < 0.05). 95.1% of infants (n=101) began to be weaned 4 to 6 months. 83.1% of infants were fed home-made weaning foods. 66.7% of infants were fed rice gruel, 18.5% of them were fruit juice, 6.2% of them were mixed grain, and 4.9% of them were commercially prepared weaning foods as their first supplementary foods. As main supplementary foods, 32.8% of infants were fed vegetable, 30.5% of them were rice gruel, and 27.7% of them were fruit juice. Mothers` nutritional knowledge related to weaning was significantly higher among mothers of college/university graduate than mothers of high school graduate (p < 0.05). 86.1% of mothers disagreed with the questionnaire in which breast-fed infants aged over 4 months needed to be fed iron sufficient food. For the improvement of nutritional status especially iron nutritional status of infants, nutritional education for mothers with weaning aged infants has to be increased and related programs have to be operated effectively. (Korean J Community Nutrition 10(4): 453~461, 2005)