A prospective survey of a family, some of whose members were suffering from keratoconus, has been assisted by estimating serum levels of total and specific immunoglobulin E. In this family of twelve there were initially 2 keratoconus sufferers identifiable clinically, and they both had raised serum levels of total and specific IgE. Of three other younger siblings with high levels of IgE 2 have become, over the course of the study period, patients requiring regular review due to established early keratoconus. The third, as yet, has no clinical evidence of altered corneal stroma. We consider, therefore, estimation of total and specific serum immunoglobulin E to be an objective test with the potential for indicating high risk patients within selected groups. The patients thus identified may have established keratoconus or may progress to develop the condition.