As in other Western countries in the Netherlands during the first half of the twentieth century, large numbers of school children were sent to holiday camps or "health colonies" to gain weight and recover strength. At first this large-scale hygienic enterprise was led by teachers, who wanted to "save" poor, undernourished children by providing a "healthy refuge" from the city. A few weeks of sunshine and fresh air at the seaside or in the woods was supposed to promote health and happiness and to improve morals. However, from 1920, stimulated by government subsidies, the colonies came under the authority and control of the medical profession. Consequently, criteria for admission were narrowed to purely medical reasons, particularly the prevention of tuberculosis, and the aims of the "treatment" to physical improvement. In the process of medicalization of ordinary children's lives the intermediate category of "weakness" (between healthy and ill) seems to have played an important role, justifying a massive philanthropic effort long after tuberculosis had stopped being a serious threat. Paediatricians created a somatic culture around the child's body, which was replaced by a psychiatric culture around children's emotions. This shift was stimulated by a second wave of medicalization focusing on mental health. Finally, a critical counter-discourse, nourished by psychoanalysis and the improved health condition of children, dispelled the illusion that sunshine and fresh air were medicine. (Contains 2 figures and 69 footnotes.)