Nurses care for elderly patients at home and in nursing homes but there is lack of data on the caring problems encountered, their causes and the solutions adopted. The aim of the study is to produce the epidemiology of such problems and, at the same time, focus nurses' attention on their causes and avoidability. The process of definition of caring problems (the focus of the study) and the discussion that brought to the draft protocol are described. The final protocol (presented with the data collection forms) is articulated in two phases: a prevalence survey through a random sampling of points estimates in index days over 6 months; a prospective registry over the same period of time of all causes perceived as clinically relevant by the nursing personnel, who will document the suspected risk factors and causes (including specifically drug therapy), and the interventions and measures which are activated.