Iris melanosis is an unusual condition characterised by the presence of minute, discrete, pigmented elevations arising from the anterior surface of the iris. We encountered two unrelated Mexican families in which all children, but no parent, had varying degrees of the condition bilaterally. Some family members also gave findings suggestive of ocular hypertension. No family member had any other ocular or cutaneous pigmentary changes with the exception of a hairy naevus on the thigh of one member. To our knowledge these are the first families reported with more than one member having isolated iris melanosis. This is also the first report of a possible relationship with ocular hypertension. Finally we suggest that the term 'melanosis' may be a misnomer, since the condition is characterised not by abnormal iris hyperpigmentation but by discrete, round elevations on the anterior iris surface.