This semester I have been developing a travel management system in Ruby on Rails. Currently at the department a partly electronic and partly paper based system is in use. I had to change it into a clearly electronic, web based system. The travel management system has two sections. The travel cost itinerary and the cost accounting. My part was the payoff part. The itinerary costs are planned costs, the accounted costs the real costs. The Ruby on Rails is a popular web framework, based on the Ruby programming language. It is object oriented and uses the model – view –controller architecture. With Ruby on Rails we can develop web applications simply and quickly. Before I planned the new system, I had to understand the old one. During the development I had to cooperate with my colleague, who developed the other part of the system. I used UML diagrams to plan the system. I made class diagram, sequence diagram and use-case diagram. After it, I implemented the program. I created the classes in Ruby and implemented them. I made some functional tests to show that the system fulfils the requirements. Results revealed that the system can perform its task, which is to replace the currently used system. I also tested the speed of the system to find out if it is usable with large amount of data. It passed my test; the generation time did not increase, even in case of large number of users. Regarding the improvement of the system, I had made recommendations based on the feedbacks.