Human reliability (HR) and the human aspects of software development have mostly been two separate areas of research. In the authors' opinion, a lot of the research going on in the area of human reliability and human factors is important for the software development process. In this paper, we present data from 13 Norwegian small or medium enterprises that develop software. The data has been collected using focus groups and are coded using a coding scheme from human factors research. In addition, we also coded the data related to development phase such as programming – and problem causes such as time pressure. The most important results are that the suggested HR scheme worked well both for error categories and for suggested mitigations. The main findings from the human factors point of view are that most errors are caused by lapses and lack of knowledge. The most error prone software development activities are programming and program changes. The most frequent cause for errors – both during programming and changes is time pressure. Based on these findings and the actions suggested by human factors theory, we suggest a set of mitigating actions for software development companies.