Mass migration leads to problems with language and cultural integration and has significant medical implications. The effect of interpreters on the diagnosis of mental diseases and ill-defined conditions was investigated in the primary care department of the Riyadh Al Kharj Hospital Programme, Saudi ArabiTwo groups of general practitioners working in the same health centre with the same patients were compared--10 Arabic-speaking and 10 non-Arabic-speaking. No differences in diagnosis were found that could be attributed to the use of interpreters, although there was a significant difference between experienced and less experienced doctors. The reasons for this finding are discussed, along with suggestions for the organization of an interpreting service.