Atopic eczema is most commonly diagnosed in children under the age of 5 yr. Environmental factors during pregnancy or in early life may confer risk for childhood atopic eczema. The present prospective study examined the relationship of the perinatal home environment and the risk of suspected atopic eczema among Japanese infants under the age of 1. Study subjects were 865 parent-child pairs. The term 'suspected atopic eczema' was used to define an outcome based on our questionnaire at 2-9 months postpartum. Adjustment was made for maternal age, gestation, family income, maternal and paternal education, maternal and paternal history of asthma, atopic eczema, and allergic rhinitis, time of delivery before the second survey, baby's older siblings, baby's sex, and baby's birth weight. A high mite allergen level from maternal bedclothes and mold in the kitchen during pregnancy were significantly associated with an increased risk of suspected atopic eczema. Frequent vacuuming practices during pregnancy and giving the infant a bath or shower at least once a day were significantly inversely related to the risk of suspected atopic eczema. Maternal smoking, maternal use of a synthetic duvet and pillow, carpet use in the living room and maternal bedroom, indoor domestic pets, no ducted heating appliance, and gas use for cooking during pregnancy and household smoking in the same room as the infant, infant's synthetic duvet, carpet use in the infant's room, or vacuuming the infant's room were not related to the risk of suspected atopic eczema. High house dust mite allergen levels and mold in the kitchen during pregnancy may increase the risk of infantile atopic eczema, whereas frequent vacuuming practices during pregnancy and giving the infant a bath or shower at least once a day may protect against infantile atopic eczema.