A registration study from clinical practice was set up to assess the prognostic value of symptoms and laboratory data at first visit for doctor-diagnosed 'asthma' in early childhood. A total of 419 children aged 0-4 y, who were newly referred to the outpatient department of the Juliana Children's Hospital with possible asthma were enrolled over a 2-y period. Data from history taking, physical examination, laboratory tests for atopic status at first visit and data from follow-up visits were recorded. Two years after the first visit all medical records were reviewed for diagnostic label. The age groups 0-1 y and 2-4 y were analysed separately, because respiratory symptoms are often transient and sensitization to inhalant allergens is uncommon before the age of 2 y. The clinical diagnosis 'asthma' was made in 113 of 231 (49%) children aged 0-1 y and in 144 of 188 (77%) children aged 24 y. Characteristics from history taking indicated shortness of breath was the most prognostic symptom in both age groups. Eczema, wheeze and non-allergic provoking factors (weather conditions) were further predisposing factors in the 0-1 y group, as were allergic provoking factors (inhalant allergens) and absence of ear-nose-throat-history in the 2-4 y group. Adding laboratory data to history total serum IgE had prognostic value, but specific serum IgE against inhalant allergens (Phadiatop) was a strong predisposing factor, especially in the 2-4 y group. These prognostic characteristics may enhance early recognition of asthma in infants and improve asthma care in clinical practice.