OBJECTIVES To find the reasons for prescription of Ticlopidine, which acts against the aggregation of platelets and is catalogued as "with hospital diagnosis", and to evaluate the criteria for its correct use and whether it is actually used in Spain to treat authorised symptoms. DESIGN A descriptive, crossover and retrospective study. SETTING Primary Care districts in the catchment area of the Virgen del Rocío hospital in Sevilla. PATIENTS Those who requested permits for Ticlopidine prescriptions, documented by the clinical report. MEASUREMENTS AND MAIN RESULTS The following data were recorded from the clinical reports presented when the Ticlopidine prescription permits were requested: patient's identification, diagnosis, pharmaceutical speciality, dosage, length of treatment and recommendation of haematological check-ups. Out of 407 reports available, the diagnosis corresponded to one of the authorised symptoms in 50.6% of cases. In a third of the patients the recommended dose was half that endorsed by the published clinical trials. Only in 2.7% of cases was mention made of the desirability of having haematological check-ups to forestall possible adverse reactions. The possibility of a counter-indication to Acetylsalicylic acid was only rarely mentioned. CONCLUSIONS Ticlopidine is recommended in 50% of cases for symptoms for which it is not authorised in our country: moreover, in 35% of cases, at doses lower than those established as effective. The information given by the doctor who initiates the treatment is usually insufficient. There is a need to reassess whether cataloguing a medicine as "with hospital diagnosis" aids its rational use.