The prescription is the legal document that defines the patient’s drug therapy, thus it must be intelligible and readable to allow the dispensation of the correct drugs to the patient in the right dose, route of administration and quantity. Incomplete and illegible prescriptions lead to misunderstanding and consequently, medication errors, which may cause from ineffectiveness to serious adverse reactions. Hence, this study aimed to evaluate the legal aspects of drug prescriptions subject to prescription retention in a Basic Health Unit (BHU) of Joinville (Santa Catarina state). For this purpose, the adequacy and legibility of information concerning patients, prescribers, and psychotropic and antimicrobial drugs of the prescriptions dispensed by a BHU from July 15 to August 15, 2018, were analyzed totaling 500 prescriptions, of which 250 were psychotropic and 250 were antimicrobial, about 17% handwritten and 83% typed. No prescriptions mentioned the patients' telephone number and few prescriptions omitted gender and address, especially the handwritten ones. Concerning the prescribers' data, few omissions were observed, related to their contact data. All drugs were prescribed in the Brazilian Common Denomination (BCD), and all psychotropic prescriptions had no omissions of route and quantity, while the handwritten prescriptions of antimicrobials comprised 10-15% omission of these data. Regarding legibility, less than 5% of the prescriptions were partially readable and an even smaller proportion were illegible. Non-standardized abbreviations were observed in 55,6% of the prescriptions. Data allow observing that, although some errors still persist the adoption of typed prescription minimized the problems of legibility, but not the omission of information. The improvement of the prescribing writing applications can also help to minimize omissions and make the prescriptions more comprehensible and ensure adequate guidance on the rational use of medicines.