Worldwide, tuberculosis (TB) kills nearly 2 million people annually, yet rapid diagnosis still relies on a 100-year-old method of sputum staining for acid-fast bacilli. The advent of solid phase micro-extraction and gas chromatography/mass spectrometry makes it possible to systematically investigate whether volatile metabolites from organisms belonging to the genus Mycobacterium can be used as a rapid and highly selective alternative to the traditional diagnostic methods. We have identified four specific compounds (methyl phenylacetate, methyl p-anisate, methyl nicotinate and o-phenylanisole) from Mycobacterium tuberculosis and Mycobacterium bovis cultures grown in vitro that are distinctive volatile markers. These compounds are detectable before the visual appearance of colonies, potentially useful as the basis of a non-invasive diagnostic test for TB and have characteristic odors.