In our questionnaire study of 599 six-month-old and 512 twelve-month-old infants born in Western Sweden, we found that parents continued to adhere to outdated primary preventive recommendations against introducing eggs and fish early in the diet. Thirty-five percent of parents had not introduced eggs and 15% of the parents had not introduced fish by the time the infant was ten months old. We could also confirm a high prevalence of wheezing. At twelve months, 17.6% had had one or more episode of wheezing. Of the twelve-month-old infants, 4.1% had received or were being given inhaled corticosteroids. Twenty-five% had or had had eczema at twelve months. 11% had been admitted to a neonatal ward and one-half of these had then been given broad-spectrum antibiotics (5.9% of all twelve-month-old infants in the study). 37% of the households kept fur-bearing pets. We believe that the questionnaire used in this study can be a useful instrument for estimating the effects of lifestyle and environmental factors on the development of future asthma and allergy.