Volatile sulphur compounds (VSC), hydrogen sulphide, methyl mercaptan and dimethyl sulphide are by-products derived in oral cavity through putrefactive activity of microorganisms. VSC are the principal cause of physiological oral malodour. There are indications that these compounds are cytotoxic to oral tissues. Hence, it has been considered that the prevention of oral malodour has an important role in preventive dentistry. The objective of this study is to ascertain the effect of two mouthwashes, sodium azulenesulphonic acid and povidone-iodine, which are frequently used in dental clinics, on concentration of VSC in mouth air. The VSC were analyzed using VSC analysis system. VSC were determined at immediately after rince and at one, two and three hours after rince. The results indicated that neither mouthwash was very effective in controlling VSC production. No reduction in VSC was observed at one and two hour post-rinsing with sodium azulenesulphonic acid mouthwash, and only 39% reduction of total sulphur of VSC was observed at one hour following the use of the povidone-iodine containing products. However, this effect was lost within two hours post-rinsing.