Abstract Caffeine is a land-based pollutant. It was detected in Tasköprü stream, a well in Yalova city and Sea of Marmara. Caffeine is existed in the thea and metabolized after taken into human body in ratio of 99%. The source of caffeine in aquatic system is the unconsumed thea discharged to the stream and sea. This is the main cause for the poIIution of environment. Its identification in marine indicates anthropogenic inputs.