The new multiple puncture tuberculin testing device, 'Imotest', was compared to the Mantoux test (10 I.U.) in an Australian population. The tests were applied simultaneously to opposite forearms of 105 volunteers. Sixty-eight per cent of the Mantoux tests were positive compared to 39% of the 'Imotests', resulting in a false negative rate of 44% and the difference was highly significant. A further 30 volunteers were tested with a different batch of 'Imotest' and similar results were obtained. When multiple 'Imotests' were applied simultaneously to each of two subjects in a separate study, there was a wide variation of response within each subject, and positive and negative reactions occurred side by side. These results indicate that the 'Imotest' is significantly less sensitive than the Mantoux test and is unsuitable for use as a diagnostic or screening test.