The complex-type chlorine-based disinfectant cleaner is a tablet-type agent which is dissolved in 500 mL of tap water, and the prepared solution (0.1% of available chlorine) displays a light red color. The stability and color degradation of the prepared solution were examined. The prepared solution was put into airtight glass containers and stored under the following conditions: 1) under room light at 23℃ to 30℃, 2) under direct sunlight at 24℃ to 34℃, 3) under shaded conditions at room temperature, 4) under shaded conditions at high temperature (40℃), and 5) under shaded conditions at 4℃. The available chlorine concentration (measured by an iodine titration technique), pH, and absorbance at 520 nm of the prepared solution were measured immediately, and 3, 7, and 14 days after preparation. The available chlorine concentration and pH of 0.1% sodium hypochlorite solution were measured as controls. The available chlorine concentration of the prepared solution fell under the various test conditions to 1) 71% and 58%, 2) 68% and 53%, 3) 70% and 59%, 4) 44% and 17%, and 5) 93% and 89%, at 7 days and 14 days after preparation, respectively. The temperature of the storage area clearly affected the stability of the prepared solution. pH, absorbance, and available chlorine concentration of the prepared solution were all reduced. Moreover, the color degradation of the prepared solution reflected the available chlorine concentration. The available chlorine concentration of 0.1% sodium hypochlorite solution fell under conditions 1) 95% and 91% and 2) 54% and 32%, at 7 days and 14 days after preparation, respectively, but not under conditions 3), 4), and 5). The available chlorine concentration of 0.1% sodium hypochlorite solution fell under direct sunlight, but pH was almost constant under all conditions. These findings show that the available chlorine concentration of a prepared solution falls gradually at room temperature, and the prepared solution retains the required properties for one week. However, high temperature storage must be avoided. In addition, the decrease of available chlorine concentration is well reflected in the color intensity, so that the residual available chlorine concentration can be checked by observation of the solution color.<br>