Serological tests can be helpful in diagnosing syphilis. The ideal test would be highly specific in all stages of the disease; it would be 100% sensitive and would revert to negative with treatment, thereby allowing the physician to monitor treatment effect. No single test satisfies these requirements. Being alert to the signs and symptoms of syphilis in all its stages and familiar with the meaning of the common serological tests (VDRL, MHA-TP, FTA-ABS) will help physicians to detect early treatable disease and thus prevent tertiary syphilis or spread to others. This article describes the serological tests used to diagnose syphilis and outlines what to look for if a VDRL is reported as reactive.