Human saliva can be easily obtained by noninvasive techniques and contains many analytes of interest for screening, diagnosis and monitoring. These include steroid and other nonpeptide hormones, therapeutic drugs, drugs of abuse and antibodies. Numerous studies in the past 40 y have shown correlations between serum and saliva levels. Both diurnal and monthly profiles of hormone levels parallel traditional serum patterns. Multiple specimens for steroid hormone analysis can be easily collected by the patient, at home, to monitor fertility cycles, menopausal fluctuations, stress and other diurnal variations. Drug doses can be monitored without inconvenient and costly visits to blood-drawing facilities. Antibody levels can be determined to screen for infectious diseases. Saliva can be collected directly by spitting into a tube or with one of several devices, each of which has its own special advantages and disadvantages. Salivary levels of steroid hormones and other analytes that are protein bound in serum reflect the unbound and active concentration of the hormone. Saliva can be used as a diagnostic specimen not only to obtain information more inexpensively and efficiently than serum, but also to provide information not readily available from serum testing.