The PhonePages of Sweden is a company that develops software for mobile units, especially cell phones. This thesis treats the development of, and contingencies for, a mobile phone directory, using the limited resources found in a mobile unit. The project was implemented and executed at The PhonePages with the intention of creating a product to sell to a third party.By studying different solutions, their benefits and drawbacks, an abstract picture of the product was constructed. Problems covered include compatibility problems caused by todays platform diversity as well as problems with saving, organizing and presenting data.The main goal was to create a phone directory which does not make external information retrievals. The service should contain both company and personal information, with name and phonenumber.