Background: Unused medicines in households are among the problems in many modern societies and developing nations. This issueleads to social and economical problems, and it is associated with other complications such as self-medication, poisoning, incompleterecovery, and suicide.Objectives: The present study was carried out in Mashhad and aimed at determining the amount of unused medicines in Mashhadihouseholds in 2013.Patients and Methods: In a cross-sectional study in 2013, three hundred households were selected through a cluster random samplingwith the help of 12 healthcare centers in Mashhad. Data were collected by applying a checklist and analyzed by SPSS 11.5. Descriptiveindices, including central tendency and dispersion, and frequency distribution were applied to describe qualitative variables; and chi-2, Man-Whitney, and Kruskall-Wallis to compare quantitative variables. Level of significance was set to P < 0.05.Results: This study showed that the existence of unused drugs and the number of unused drugs in household have significant differencein four zones (P = 0.01, P < 0.001). Also, health insurance coverage was statistically different in various health centers (P = 0.002).Also, there is a significant association between unused medication in the household and family size, father’s occupation, and a familymember being a health professional, respectively (P value 0.02, 0.002, 0.04)Conclusions: The findings of this study and similar ones support that the amount of unused medicines inside houses has to be loweredby physicians prescribing a more reasonable number of drugs, giving consultation to patients, and raising public awareness. On theother hand, a mechanism needs to be applied in order to make use of the drugs kept inside houses and reduce drug wastage.