The STD (Sexually Transmitted Disease) Clinic is a Public Health-Seattle & King County service that provides confidential STD and HIV evaluation, screening, testing and treatment on a sliding-fee scale.? The STD Clinic can be accessed on a walk-in basis. If you need to be seen later than 3:30 p.m., please call our clinic to make sure we are still accepting patients for the day or contact the King County clinic website.