Pursuing our studies about the beginning of the family treatment, the present research aimed at investigating the period of preliminary interviews with families. An effort was made to focus on the diagnostic evaluation of the family motivations to seek for psychotherapeutic help as well as on the implications of constructing the conjoint demand and its influence on the family adherence to the treatment. The conjoint family demand was a notion developed in this study, meaning the latent motivation shared by all the family members which led them, conjointly, to look for psychotherapy. In other words, it corresponds to the interpsychic contents that are still incomprehensible to the family. It is assumed that during the period of interviews it is important to raise the problematical issue of the initial complaint, focused on the existing conflicts with the identified patient. These initial interventions seek the transformation of the family’s position as victims to a conjoint positioning, responsible for the maintenance of their suffering. Special emphasis was also given to the value of using evaluation instruments, considering them as a resource that contextualizes the psychotherapist’s hypothesis and promotes an increase of the family’s associative chain. This investigation described exclusively the Family Art Evaluation in order to disseminate it even more in Brazil as a complementary instrument to the family diagnostic evaluation. To achieve the proposed objectives, three clinical cases, with different complaints and problematical issues, were described. They illustrated both the period of interviews and the work in constructing the family conjoint demand, whose analyses were intended to contribute to the enrichment of the initial work of the family psychotherapy.