Background: Telephone nursing in primary healthcare has been suggested as a solution to the increased demand for easy access to healthcare, increased number of patients with complex problems, and lack of general practitioners. Registered nurses’ assessments may also be of great importance for antibiotic prescriptions according to guidelines. The aim of this study was to describe registered nurses’ views of telephone nursing work with callers contacting primary healthcare centres regarding respiratory tract infections.Methods: A descriptive, qualitative study was performed through interviews with twelve registered nurses in Swedish primary healthcare. Results: The overarching themes for registered nurses’ views on telephone nursing were captured in two themes: professional challenges and professional support. These included three and two categories respectively: Communicate for optimal patient information; Differentiate harmless from severe problems; Cope with caller expectations; Use working tools; and Use team collaboration. Optimal communication for sufficiently grasping caller symptoms and assess whether harmful or not, without visual input, was underlined. This generated fear of missing something serious. Professional support used in work, were for example guidelines and decision support tool. Colleagues and teamwork collaboration were requested, but not always offered, support for the interviewed registered nurses.Conclusions: The study deepens the understanding of telephone nursing as an important factor for decreasing respiratory tract infection consultations with general practitioners, thus contributing to decreased antibiotic usage in Sweden. To cope with the challenges of telephone nursing in primary healthcare centres, it seems important to systematically introduce the use of the available decision support tool, and set aside time for inter- and intraprofessional discussions and feedback. The collegial support and team collaboration asked for is likely to get synergy effects such as better work environment and job satisfaction for both registered nurses and general practitioners. Future studies are needed to explore telephone nursing in primary healthcare centres in a broader sense to better understand the function and the effects in the complexity of primary healthcare.