The toxicity of arsenic has been known for centuries, and its presence in drinking water is a huge problem for millions of people. Increased concentration of arsenic was found in drinking water of eastern Croatia. High arsenic concentration can cause many diseases, and can cause nerve and skin damage and increase the risk of cancer. Most common methods for arsenic determination in drinking water are spectrometric. Silver diethylditiocarbamate spectrophotometric methods with sodium borohydride or zinc are used for reduction of arsenic to arsine, which is determined spectrophotometrically. Modern methods for arsenic determination are inductively coupled plasma in combination with mass spectrometry and inductively coupled plasma in combination with atomic emission spectroscopy. Methods for arsenic removal are conventional methods, adsorption processes and membrane processes. Conventional methods are coagulation, softening and Fe/Mn removal. Adsorbents for removal are metal oxides, activated alumina, activated carbon, ion exchange, etc. Direct removal with high pressure membrane processes is possible as well as combined removal by adsorption and low pressure membrane processes.