The era of cross-sectional "snapshot" clinical epidemiology studies in consultation-liaison psychiatry, while still important, do not in themselves yield the critical outcome information needed to document both the clinical efficacy and cost-efficacy of timely psychiatric treatment of patients with concurrent medical-psychiatric illness. As consultation-liaison psychiatry has been plagued by problems regarding reimbursement for clinical services rendered and has only a few systematic outcome studies as yet documenting the effectiveness of treatment interventions, more prospective studies are desperately needed to confirm the value of our efforts. The era of proselytizing the virtues of consultation-liaison psychiatry is over, and as with every other area of psychiatric therapy, governmental policy makers and third party payors are appropriately demanding to see "proof" that our treatments are both clinically- and cost-effective. As may be seen from this brief overview of our research demonstrating the potential reversibility of disabling cognitive dysfunction in depressed medical-psychiatric patients and the efficacy of labetalol in decreasing cardiovascular complications from ECT in high risk medical patients, positive reports from clinical investigations that are strategically planned and implemented on specific populations form strong arguments for the clinical and probable cost efficacy of both consultation-liaison psychiatry and medical-psychiatric units.