Abstract. All types of medication errors including missed doses, incorrect dosage forms, time intervals, and routes are essential encumbrances for qualitative pharmaceutical care and security of medicine [1]. Problems related to prescription errors are common in the healthcare profession, and are responsible for significant increase in costs, cases of morbidity and mortality [2]. The aim of the study was to analyze the common errors in prescriptions which were received in pharmacies and their effect on the security of medicine. Retrospective study was conducted between December 2013 and January 2014 in the pharmacy of Riga, Latvia. Prescriptions were analyzed to identify errors in Inscriptio, Praescriptio and the Signatura part. Of 200 prescriptions, only 14 (7%) were filled correctly according to the legislative requirements in Latvia. The most common drug therapeutic class in the prescriptions was non-steroidal anti-inflammatory drugs (NSAID) and other analgesics (21.1%). Unclear handwriting was observed in more than one third of all studied prescriptions (n=72; 36.0%). Mean age values of physicians were higher, but not significantly different, in the unclear compared to clear prescriptions, 59.5 ± 8.5 vs. 57.8 ± 10.6, respectively (p=0.253). Omission of the quantity of drug in the prescription part was the most frequent type of the error (n=112, 56.0%). High level of incorrect prescriptions was found during the period of study in the pharmacy. Overall, approximately 27% of prescriptions had significant failures, which could negatively affect therapeutic effect and safety of drug use.