Objectives: The aim of this study was to evaluate the relationship between the results of penicillin hypersensitivity testing and the demographic characteristics of the subjects, the characteristics of the primary reaction to penicillins, the existence of hypersensitivity to other allergens, existing comorbidities and family history of penicillin hypersensitivity. Study design: The study was conducted as a cross-sectional study. Subjects and methods: The subjects were patients tested for hypersensitivity to penicillins in Clinical Pharmacology outpatient clinic at the Clinic for Internal Diseases as a part of Clinical Hospital Center in Osijek, in the period from January 1, 2016 to December 31, 2019. Data for a total of 50 subjects were collected from archival medical records. The collected data, including demographic, outcomes of in vitro and in vivo testing for penicillins, data on the primary reaction and other existing allergies, comorbidities and family history of penicillin hypersensitivity, were analyzed in relation to the outcome of testing. Results: Out of the 50 subjects, 36 % had a positive penicillin hypersensitivity test (skin test or drug provocation test). Angioedema as a possible clinical manifestation of the primary reaction was significantly more recorded in patients with a positive test outcome. Age, sex, primary reaction characteristics including the type of hypersensitivity reaction, clinical manifestation with the exception of angioedema, administered antibiotic and time passed until testing as well as existing comorbidities and hypersensitivity to other allergens and family history of penicillin hypersensitivity did not show a significant difference in relation to the outcome of testing. Conclusion: Given that 36% of the subjects had a positive test outcome, it is important that this hypersensitivity testing allowed the rest of the subjects to use penicillin safely in the future. Personal history and characteristics of the subjects did not prove to be highly predictive towards the outcome of testing.