We are developing and testing a small, efficient time-of-flight mass spectrometer to rapidly identify important biomarkers for human space exploration. We are also evaluating critical biomarkers that are indicators of muscle atrophy and bone demineralization associated with space travel. We have recorded mass spectral signatures of several biomarkers. Compounds under investigation include: insulin-like growth factors (IGF-I), urinary 3-methylhistidine, estradiol, and creatinine. We have also completed initial studies of trivalent hydroxypyridinium crosslinks which are excreted as free pyridinolines in urine during bone resorption.