The apparent dry‐heat resistance ofB. subtilisvar.nigerspores in contact with serum albumin, certain carbohydrates or lipids, was determined in an open test system. The resistance, in terms of D160‐value, was significantly increased by sucrose or serum albumin and decreased by glucose or fructose. The D160‐value of spores heated in contact with olive oil and triolein was about the same as that of the control spores (clean spores). The D160‐value of spores in soybean oil, tricaprin or trilaurin was, however, somewhat higher than that of the control spores. The D160‐value for spores heated in different lipids increased in the order: olive oil