Breath tests are increasingly entering into medical diagnostics because of their non-invasive nature. However, a substantial breakthrough in breath testing is hampered by available instrumentation that is bulky, expensive and often not capable of real- time analysis. Isoprene is a volatile organic compound present in human breath. This endogenously formed substance is an indicator with non-invasive diagnostic potential. It has been related to cholesterol biosynthesis and may be used for mass screening of lipid disorders. Significantly, it has the potential to be applied in cancer screening. Vista Photonics, Inc. proposes to develop a compact, real-time medical isoprene breath analyzer. A specially designed laser source based on an external cavity diode laser will be developed. A derivative photoacoustic spectroscopy approach will be applied to achieve the required selectivity. This new optical instrument will allow selective determination of the isoprene concentration while suppressing other interfering breath components. This enabling feature will allow the analysis of untreated breath samples, which substantially reduces instrument complexity. The proposed instrument platform is especially suited to be applied for the selective optical detection of larger molecules possessing broad absorption bands. The high performance detection of these molecules may find widespread application beyond medical applications. The development of a high performance respiratory analyzer for detecting the critical breath component isoprene is proposed. This non-invasive medical diagnostics tool may be used for mass screening of lipid disorders and as well as cancer screening. [unreadable] [unreadable] [unreadable]