The authors intended to develop a new sort of inhibitor for mold growth in tempera paintings. As a preliminary experiment, 2-18 species of fungi, e.g. <i>aspergillus, aureobasidium, phoma, penicillium</i> and <i>toricoderma</i> families, were isolated from the surfaces of paintings, painted by students of the Sokei Academy of Fine Arts, as part of their training program for tempera technique, and they were used for investigations for two reagents, 2-(4-thiazol)-benzi-midiazol (TBZ or thiaben) and 4-chlorophenyl-3-iodopropalgyl-formal (IF1000), evaluating their capacity. These two fungicides can be considered to be of low toxicity and can be used safely. By adding 10 parts per million of TBZ or 1 part per million of IF1000, satisfactory results can generally be observed, but for some strong fungi, more than 100 parts per million of TBZ or 2.5 parts per million of IF1000 should be applied for effective results. From the results, a suitable recipe for inhibiting mold growth in tempera paintings can be planned and good results obtained.