The use of geographical data is increasing in real world applications and due to this, Geographical information systems (GIS)are a growing interest area for research nowadays.Today, GIS is combined with the world wide web to provide information to alot of people. Web-based GIS applications have gained popularity because of their easy use and simplicity. Usability evaluation is becoming important part of interaction design to find out various usability isses in applications. In this study, two web-based GIS applications i.e. Google maps and MapsQuest are evaluated to find out usability issues.To accomplish the main goal of this study, differnt techniques have been used.Special creiteria are adopted for usability evaluation. Usability tests are performed on six graduate users, questionnaires are filled by these users and interviews were conducted to validate the results. The authors have provided a number of suggestions based on the problems that were identified in this study for google maps and MapsQuest to improve the usability of these applications.