The estimation of effort and cost is still one of the hardest tasks in software project management. At the moment, there are many techniques to accomplish this task, such as Function Points, Use Case Points and COCOMO, but there is not much information available about how to use those techniques in non-waterfall software lifecycles such as iterative or spiral lifecycles projects. This paper shows the results obtained when applying a technique to estimate the effort of each construction iteration in software development projects that use iterative-incremental lifecycles. The results were obtained from software projects of a fourth-year course in Informatics. The technique proposes the use of Function Points and COCOMO II. © 2006 IEEE.