Flow-volume measurement is the most frequently used pulmonary function test in childhood. Recent studies have shown that even pre-school children are often able to perform the maximal effort in breathing required for this test. The conditions and criteria for reliable measurement of flow-volume curves in 3-6 year-old children are reported. We have also presented the reference values published for this age group, and discussed problems associated with interpreting results. This review will hopefully encourage our children’s hospitals to use spirometric testing in pre-school children in both clinical practice and research.