The aim of this study was to determine whether a low dose of ultrasound, applied over the mastoid bone, caused a subjective improvement in the level of tinnitus in long standing tinnitus sufferers. Forty patients from the Swansea Tinnitus Association volunteered to take part in a double blind crossover trial. They received a 10-minute treatment with an ultrasound generator and an identical placebo device on two separate visits. The devices were randomly allocated on the first visit. At each visit the patient noted whether their tinnitus was completely improved, slightly improved, unchanged or made worse by the treatment. Forty per cent of patients who completed the trial were improved by ultrasound, 7% by placebo. Low powered ultrasound was significantly better at producing improvement than placebo (P less than 0.02 Binomial Test).