Background: Healthcare personnel (HCP) often experience undesirable working conditions. Risk behaviours for organism transmission can lead to healthcare associated infections and risk behaviours has been described to be influenced by working conditions. Research is lacking regarding HCPs working conditions and its relation to risk behaviours for organism transmission which this thesis aims to investigate.  Methods: Study I had a mixed-methods convergent design. Observations and interviews were performed with 79 HCP, i.e., registered nurses (RNs) and assistant nurses (ANs). First-line managers were interviewed about the unit´s overall working conditions. The qualitative and quantitative data were analysed separately and then merged. Study II was a cross-sectional study with 417 RNs and ANs. The questionnaire included: self-efficacy to aseptic care, structural empowerment (SE), work engagement (WE) and work-related stress (WRS). Correlational analysis and group comparisons were performed.  Results: In Study I risk behaviours frequently occurred regardless of measurable and perceived working conditions. The HCP described e.g. staffing levels and interruptions to influence risk behaviours. In the statistical analyses, risk behaviours were more frequent in interrupted activities and when the HCP worked together. In Study II the HCP rated high levels of self-efficacy to aseptic care. Differences were found between self-efficacy and some of the grouped working condition variables and definite but small relationships were found between self-efficacy to aseptic care and SE/WE/WRS.  Conclusion: The HCP rated high levels of self-efficacy to aseptic care, but on the other hand, risk behaviours frequently occurred irrespective of working conditions. Healthcare managers are responsible for HCPs work environment and should continuously work to promote sufficient working conditions and to increase HCPs understanding of risk behaviours, which consequently also promote patient safety.