Current tests for the diagnosis of interstitial cystitis (IC) are reviewed, including clinical assessment, urodynamic testing, cystoscopy, bladder biopsy, and urinary markers. A MEDLINE search was performed of all studies dealing with the diagnosis of IC. These studies were critically reviewed with the goal of arriving at a utilitarian approach to IC diagnosis. IC is being diagnosed with increasing frequency. However, the diagnostic criteria are nonuniform and there is significant overlap between chronic pelvic pain syndromes in men and women and IC. Diagnosis of IC can be made clinically and by cystoscopy and hydrodistention. The sensitivity and specificity of urinary markers have not been prospectively studied. Individual practitioners continue to use the various diagnostic tests. There is a clear need for uniform diagnostic criteria for clinical diagnosis as well as epidemiologic and research studies.