This paper describes two different optoelectronic detection techniques: cavity-enhancedabsorptionspectroscopyandphotoacousticspectroscopy.Thesetech- niques are designed to perform a sensitive analysis of trace gas species in exhaled human breath for medical applications. With such systems, the detection of patho- genic changes at the molecular level can be achieved. The presence of certain gases (biomarkers), at increased concentration levels, indicates numerous human diseases. Diagnosis of a disease in its early stage would significantly increase chances for effec- tive therapy. Non-invasive, real-time measurements, and high sensitivity and selectiv- ity, capable of minimum discomfort for patients, are the main advantages of human breath analysis. At present, monitoring of volatile biomarkers in breath is commonly useful for diagnostic screening, treatment for specific conditions, therapy monitoring, control of exogenous gases (such as bacterial and poisonous emissions), as well as for analysis of metabolic gases.