Four simple multiple-choice questions about tuberculosis (TB) were posted on a non-medical internet site for a 2-month period. A total of 564 responses were received. Sixty-two were excluded as individuals had made multiple attempts at the questions. Sixty-five per cent of responses were from North America, 14.5% from Europe and 12% from Australia and New Zealand, with only a small number of responses from Africa, the Indian subcontinent and South America. Of the respondents 49.5% correctly answered that cough is the commonest symptom of TB, 45% knew that TB was transmitted mainly by air-borne droplets, 37.8% knew that TB was caused by a bacterium. Only 19.5% knew that the most important risk factor for developing TB was HIV infection and only 4% answered all questions correctly. This survey suggests that knowledge about tuberculosis is limited in computer-literate individuals throughout the world.