The present work aims to investigate the phenomenon of presenteeism, a construct still little studied, especially in Italy, in its medical, psychological, social and economic implications. In the first part we propose a review of the international literature, and of the meanings, causes and consequences of the phenomenon on individual and organizational health. In the second part, we present a study which involved, for a period of about a year, 326 workers of a company in the engineering industry. This study is, in this writers' knowledge, the first survey--characterized by a longitudinal design and a multi-method approach, both not very present also in the international literature--carried out in our country on the phenomenon of presenteeism. The survey examines the mediating role of presenteeism in the relationship between specific risk factors of work context and content--career growth, conflict with colleagues, social rewards--and the psycho-physical strain. The risk factors were detected through a self-report instrument at the beginning of the year. The workers, at the end of the same year, were subjected to a healthcare surveillance visit in which the competent physician evaluated the psycho-physical strain. The hypothesized relations have been tested by estimating a structural equation model with observed variables. What emerged was a negative association between social rewards and presenteeism and a positive relation between conflict with colleagues and presenteeism. Instead, no association between growth and presenteeism emerged. Presenteeism, in turn, predicts psycho-physical strain. Overall, presenteeism mediates the relationship between social rewards and strain, as well as between interpersonal conflict and strain, but not between growth and strain. This work is characterized by some innovative aspects compared to previous studies conducted on the subject, both in theory and methodology. From a theoretical point of view the hypothesized model aims to capture specific risk factors of the process leading to the formation of work stress, through the role of presenteeism. From a methodological point of view the adoption of a longitudinal and multi-method research design allows a better understanding of the relationships between the variables investigated, often limited by the exclusive use of self-report instruments in cross-sectional designs. Finally, the possible interventions aimed at preventing presenteeism and minimizing its negative consequences on health are discussed.