Background:There is a controversial aspect concerning the method of choice for maintaining the patency of peripheral intermittent intravenous catheters. Some institutes use a dilution of heparin for this purpose, whereas many others use a small amount of normal saline flush. So, it would be worthwhile to look for the best available evidence for this. Methods: A thorough search was performed in different nursing and medical databases, in order to find the available evidence. All relevant information has been obtained from papers written in English and published during the last twenty years. Results: Many research papers were examined and appraised for their level of evidence. The available evidence suggests the same degree of effectiveness of normal saline versus heparin solution for maintenance of patency of peripheral intermittent intravenous catheters. Conclusion: Since the use of heparin is considered the cause for many side effects and complications, normal saline should be the solution of choice as it contributes to patients' safety, patients' satisfaction and cost savings.