In this doctoral dissertation all the factors that have an impact on marine pollution of the Adriatic Sea by sanitary wastewater from cruise shipswere explored and analyzed. Basic characteristics of the Adriatic Sea, maritime transport and characteristics of tourism in Croatia were explored. Cruising tourism in terms of trends in cruise traffic and in terms of sustainable development was analyzed as well as marine pollution by sanitary wastewater from cruise ships. International and national legislation related to the sanitary wastewater was analyzed and compared. A detailed analysis was made of available technology for sanitary wastewater treatment and performance of wastewater treatment systems that are used on cruise ships. A one-year survey was done in which the movement of cruise ships in the Adriatic Sea withcapacity of over 500 people was followed as well as their routes and time of entry and exit from the Adriatic Sea and from MARPOL Annex IV areas of limited wastewater discharge. Based on that survey, an original model of the cruise traffic in the Adriatic Sea was developed, which, on basis of cruise ship itinerary in acertain period of time, gives us retention times of these ships in fourteen defined geographical areas of the Adriatic Sea. This model provides the basic input parameters for the original valuation model of marine pollution by wastewater from cruise ships. Valuation model of marine pollution by wastewater from cruise ship sallows the user to simulate the pollution of the Adriatic Sea geographic areas in a variety of selected scenarios. Both developed models have been unified in a computer program Kruzeri. The program, based on the entered input parameters, gives us output parameters – quantity and quality of sanitary wastewater discharged to the defined geographic areas. The program recognizes what wastewater treatment system is on every ship in a certain selected time period and the average capacity of a ship and user can select the discharge speed of sanitary wastewater, enter the exact capacity of each ship on each cruise and select ship opration modes in each MARPOL Annex IV area of limited wastewater discharge. By changing operation modes of the ship in different scenarios, valuation model of marine pollution will enable simulation of various scenarios in order to obtain the desired or expected load values of wastewater from cruise ships on specified geographic areas which further enables the evaluation of the current legislation and the identification of critical areas considering marine pollution by sanitary wastewater from cruisers.