This research was conducted to examine the frequency of mycotoxin contamination in commercial cat foods and to examine the sensitivity of growing cats to feeds naturally contaminated with Fusarium mycotoxins. Seventy samples of dry commercially produced cat foods were tested for mycotoxins as well as conjugated (masked) deoxynivalenol (DON). Based on the results of this survey, it was concluded that commercially available cat foods are frequently contaminated with mycotoxins. An in vivo study was conducted with eight kittens (four per diet) fed one of two extruded diets for 21 days including a minimally contaminated control diet and a diet containing grains naturally contaminated with Fusarium mycotoxins. It was concluded that the feeding of diets naturally contaminated with Fusarium mycotoxins adversely affected the growth and development of kittens.