What causes a constant ringing in the ears?

Tinnitus: Tinnitus usually goes along with hearing loss. Nerve damage due to noise &/or aging often causes ringing. Medications: Aspirin or other non-steroidals (ibuprofen, aleve, (naproxen) etc.) cause tinnitus. Caffeine, nicotine, can increase tinnitus. Diuretics or certain antibiotics can cause it-- no medicine shown to cure tinnitus. Try masking noises like a fan or radio. Get ears and hearing checked.