This study, conducted in Chile with a low-income population, was designed to assess quality of mother-infant attachment in 17-21-month-old children of different nutritional status. 43 nutritionally healthy and 42 chronically underweight children were seen with their mothers in the Ainsworth Strange Situation. Children were classified in the conventional B (secure) and A and C (anxious) attachment patterns. In addition, an A/C pattern of anxious attachment was found to be frequent among children who consistently fail to gain adequate weight-for-age. Results showed a greater proportion (93%) of anxious attachments in the underweight group as compared to the group of children without a history of nutritional deficits (50%). Children classified as A/C presented the most serious weight deficits within the underweight group, indicating an association between severity of the nutritional deficits and insecure/disorganized attachments. Various hypotheses concerning the association between chronic nutritional deficits and insecure/disorganized attachments in infancy are discussed.