Preventive mental health work has for many years been a cornerstone in child psychiatric work in Sweden. Psykologverksamheten, a program at Psykiska Barn och Ungdomsvarden (PBU), is the out-patient child psychiatry unit in Stockholm County. The aim of the program is to promote infant mental health and to prevent children from becoming future patients at the psychiatric child and adolescent clinics. Located in the residential areas, the Maternal and Child Health (MCH) centers reach almost 100% of infant families and are the platform for the preventive work. The pediatric staff at the MCH centers have been encouraged to apply a psycho-social working model in which not only the pediatric but also the psychological needs of the families are considered. In regular case-consultations child psychologist have offered training and support to the medical staff. This has been bases on the theoretical assumption that if the MCH staff are better equipped in dealing with mental health issues, the support they give to infant families will improve and the referrals to the psychologist at the Psykologverksamheten will decrease. However, through the working alliance established between the MCH staff and the psychologist, the latter has become a professional "secure base," making the MCH staff more sensitive and observant than earlier. Because the Swedish welfare system is at present undergoing changes due to Government economic restraints, the stress put on families has increased. The referrals to the psychologists have almost doubled. The paper discusses the qualitative development of the relationship between the Psykologverksamheten and the MCH staff, and, with reference to a clinical vignette, discusses the importance of not only supporting general preventive work but also of specifying early dyadic therapeutic interventions.