The emergency medical services (EMS) has been described as a challenging professional practice where the persons in need of care vary greatly in terms of age, symptoms and situations. There is limited research regarding the experience of being new to this line of work, and what support new professionals desire during their first year in a professional practice like the EMS. The overall aim of this thesis was to increase knowledge about the experience of being new to the EMS and to identify what support new professionals desire during their first year. This thesis is based on the findings from four studies. The theory of communities of practice has been used for interpreting, understanding and explanation of the synthesised findings of these four studies. Qualitative research approach was used in Studies I and II, the Delphi technique was used in Study III and a quantitative research approach was used in Study IV. Data was collected using interviews and questionnaires. The findings in this thesis show that the experience of being new to the EMS is a triality of the own identity, the community and the practice and the desirable support during the first year was summarized by 11 statements of support. The own identity refers to the experiences of transitioning into a new professional identity. It is a period of mixed emotions and low self-confidence where supports that aim at strengthen self-confidence is desired. The community refers to the experience of the colleagues in the EMS. Supportive climate and a trustworthy colleague have positive influence on the own professional development and help strengthening self-confidence. Unsupportive and harsh cultures, without mutual engagement around patient care, negatively affected the experience. Supports that contribute to the new professionals feeling welcome and respected in the new community was desired. The practice refers to the experiences of the EMS assignments and the EMS context. Being able to work independently and handle unpredictability was considered challenging, and sometimes this challenge was intensified when the colleague and the new professional did not share the same view of the situation. Supports that aim at creating a sense of stability and control was desired. The thesis concludes that the experience of being new to the EMS is a triality where the own personal development of a new identity, the EMS community and the EMS practice highly influence the experience. It is important to emphasis all three dimensions of this triality when supporting new professionals in the EMS. This thesis also concludes the importance of all members of the EMS community having mutual engagement and a shared view on what, when and how the patient care in the EMS should be provided. The findings in this thesis will contribute knowledge that will be of use when designing formal support- and introduction programs for professionals new to the EMS.