The trend of contaminants was studied in thermized Lassi during storage at different temperature. At 37±2°C, the count of SPC; yeast and mold in control increased from 230x103: 10 to 400x103: 14x103 on 8th day. On the same day, L65 and L70 (SPC; yeast and mold count) was only 27x103: 500 and 10x103: 40, respectively. At the day of termination, the count was found to be 40x103: 3000 at 12th day in case of Les and 48x103: 5000 in L70 on 16th day. At refrigeration temperature (7±1°C), the count in control of SPC and yeast and mold were 310x103: 5000 at the termination 15thday, in L65 it was 61x103: 3000 on 30th day; in L70 the count was 45x103: 2500 at the day termination (35th day). Shelf life of product is directly effected by the undesirable organism present in lassi.