Various factors have been recognized to affect the viability of probiotic bacteria during storage of fermented dairy products such as pH, redox potential and acidity, buffering capacity, packaging, molecular oxygen and storage time and temperature (5, 22). Storage temperature has substantial impact on maintaining viability of probiotic bacteria and it is generally well-known that the probiotic yogurt must be kept under refrigerated storage (22- 24). However, mentioned product might be subjected to cold chain interruption for hours during industrial distribution, retailing and home storage. This leads to the question whether the number of probiotic bacteria declines to such an extent that there are not enough bacteria remaining in the product to be useful. Few studies have studied the effect of cold chain interruption during storage on the survivability of probiotics (25). In this study, the viability of probiotic bacteria in yogurts exposed to cold temperature interruption (stored at room temperature) was investigated.