Cogan's syndrome is characterized by a non-luetic interstitial keratitis associated with vertigo, tinnitus and profound deafness. Evidence of a systemic vasculitis is found in up to 50% of patients. Atypical forms of Cogan's syndrome have been described in which the ocular inflammatory disease may be more severe. We describe a case of atypical Cogan's syndrome in association with bilateral posterior scleritis. Serial B-scan ultrasound measurements of posterior scleral thickness were found to be useful in assessing disease activity, in combination with clinical findings. Combination therapy with prednisolone and cyclosporin controlled the ocular disease but the deafness was irreversible. The length of follow-up of this case highlights the frequent relapses and difficult management problems which may be faced. This multisystem disease requires the close co-operation of ophthalmologist, physician and otorhinolaryngologist. Aggressive therapeutic intervention with high-dose combined immunosuppressive agents may be necessary to control severe ocular inflammatory disease.