The diagnosis of X-linked Alport syndrome is often difficult, but the demonstration of lenticonus and retinopathy may facilitate the diagnosis in adult patients. The aim of this study was to determine the diagnostic usefulness of ocular examination in children. Fourteen families with at least one affected child were studied clinically, and COL4A5 mutations were determined. The families included 15 affected boys (median age 11 years, range 4–19 years). Two boys (13%) had renal failure, nine (60%) had a known hearing loss, one (7%) had lenticonus and five (33%) had a central (4/15, 27%) or peripheral (4/14, 29%) retinopathy. Lenticonus and retinopathy were first noted in 14 and 11 year olds, respectively. All boys with retinopathy had a hearing loss. The early onset retinopathy was associated with a severe mutation (Q1383X). Eight families (8/14, 57%) comprised only sons and mothers, and two mothers (2/12, 17%) had the retinopathy. Six boys (40%) would have been diagnosed with Alport syndrome on the basis of their own or their mother’s ocular examinations. None of the six girls (median age 8 years, range 7–14 years) had ocular abnormalities. Hearing loss is usually highly sensitive for the diagnosis of Alport syndrome, but ocular examination of boys and their mothers at the initial consultation is a non-invasive test that is helpful in up to 40% cases.