Antibiotic resistance is one of the most common problems in antibacterial therapy. Several resistance mechanisms may lead to multidrug resistance (MDR), one of them is efflux pumps. Efflux pumps can be found in both prokaryotes and eukaryotes. With this mechanism, the entry of the drug into the cell is prevented or it is pumped out of the cell, thus the internal concentration of the drug is reduced and the drug cannot effect the cell. Due to this situation, which is frequently observed in microorganisms, antibiotic resistance occurs. If the efflux pump is inhibited, drugs may have a chance to affect cells. Some chemical inhibitors or natural compounds that provide this inhibition are commonly used for in vitro studies, but due to their toxicity problems, clinical use is not generally available. In this study, it was aimed to show the presence of efflux pump activity in some clinically isolated multi drug resistant strains, namely Acinetobacter baumannii, Candida albicans, Candida glabrata, Candida tropicalis, Klebsiella pneumoniae, Providencia rustigianii, Serratia odorifera, Shigella flexneri, Staphylococcus aureus and Streptococcus pneumoniae. Ethidium Bromide (EtBr) was used to determine the presence of the efflux pump activity. A concentration range of 0.5, 1.0, 1.5, 2.0 and 2.5 mg/L was used to observe the maximum EtBr concentration effluxed out the cell. After the incubation, the results were observed under UV light. As a result, it was observed that the maximum EtBr concentration effluxed out the cell changes between 1.0 and 2.0 mg/L for all strains used in the study.