Software engineers use development methods to guarantee on-time delivery, keeping to budget and quality in their software applications. There are two kinds of development methods: plan-driven and agile methods. Both of them still have problems; these refer to resolving problems instead of thinking about them, they use informal or semi-formal artefacts and they leave consistency management to the analysts. The UNC-method (a problem-based software development method) is defined in this paper. The UNC-method is currently being developed in the Universidad Nacional de Colombia; it has been used by students from the School of Systems as part of their training in methodological software development during the last five years. The UNC-method is a mixture of well-known artefacts (i.e. UML diagrams and graphical user interfaces) and non-traditional approaches (e.g. cause-and-effect diagram, KAOS goal diagrams and pre-conceptual schemas) used in trying to overcome the aforementioned problems. A case study is also used for exemplification purposes.