The aim of the present study is to analyze the degree of compliance of the obligation to note variables in the Patients' Register (L.R.E.) as well as the coincidences between these and those included in the Clinical Histories. To This end a sample (24%) has been taken of all admissions registered in the L.R.E. during 1986. Later 5% of these cases were selected at random and the correlation between the details (Clinical History and Patients' Register) was analyzed. A high degree of compliance was observed (98-99%) for most of the variables, especially those of an administrative nature. The overall percentage of losses for the definitive diagnosis was 11.6% due to a number of different reasons. The greatest discrepancies were found in age (5.8%) and in the definitive diagnosis (5.1%). The results show that the L.R.E. represents and acceptable source of health information, bearing in mind the habitual proportions of losses and eligibility.