In the development and evaluation of a multi-ethnic inventory (the BSI) of somatic symptoms associated with anxiety and depression, symptoms were derived from psychiatric case notes of Pakistani and indigenous British patients with a clinical diagnosis of anxiety, depression, hysteria or hypochondriasis. The inventory was constructed simultaneously in Urdu and English. A pilot version of the BSI was checked against psychiatric case notes in north and south India, and Nepal. The revised BSI achieved over 90% coverage of all somatic symptoms recorded in each centre. The linguistic equivalence of the Urdu and the English versions was established in a bilingual student population in Pakistan. Conceptual equivalence of the BSI was explored using factor analysis of responses by functional patients presenting to medical clinics in Britain and Pakistan. Four principal factors (head, chest, abdomen, fatigue) were similar in both populations.