The role of psychosocial factors in the development of wheezing was studied prospectively in 100 infants with a strong family history of allergy. The entire family participated in a standardized family test when the children were 3 and 18 months of age. The ability to adjust to demands of the situation (''adaptability'') and the balance between emotional closeness and distance (''cohesion'') were assessed from videotapes by independent raters. Families rated as functional in both aspects were classified as ''functional'' and otherwise as ''dysfunctional.'' Based on records of symptoms kept by the parents and on results of physical examinations at 6 and 18 months of age, the children were classified as healthy or as having recurrent wheezing, recurrent infections, or eczema. An unbalanced family interplay was common (37%) at 3 months but did not predict development of illness. If the child remained healthy and the family did not experience any further stress, family interaction was functional 15 months later. If, however, the child acquired anxiety-provoking symptoms, such as wheezing, a high proportion of families continued or began to have dysfunctional interaction patterns. When the healthy children were 18 months of age, only 12% of their families were dysfunctional, compared with 26%, 46%, and 52%, respectively, of the families of children with eczema, recurrent infections, and obstructive symptoms (p <0.01). We conclude that dysfunctional family interaction seems to be a result rather than the cause of wheezing in infancy.