Samples of commercial cotton fiber from - the U.S. crops of 1982 through 1986 were examined under ultra-violet light to detect the bright greenish yellow-fluorescing spots shown earlier to be associated with a boll rot infection by the fungus Aspergillus flavus. As in several earlier crops, samples with these distinctive fluorescing spots were found in a high proportion of samples from El Centro, CA, and nearby Phoenix, AZ, in a smaller proportion of samples from central and southern Texas, and in an even much smaller proportion of samples from other parts of the Cotton Belt. When examined In conjunction with similar previously reported evidence from surveys of nine crops during the period 1957-1981, the data provide no indication that any clearly proven progressive change has occurred in the geographical distribution or overall proportion of samples exhibiting this fluorescence in the U.S. crop since our first survey on the crop of 1957. Boll rot infection with this semi-thermophillic fungus thus continues to be concentrated in the same exceptionally hot growing areas where it was detected earlier. An unusual situation, however, occurred in the 1980 crop, in which there was a moderate but easily detectable expansion of the infection into the mid-South and Southeast, a situation which has not been encountered again since 1980 and which is believed to have resulted from the especially hot weather prevalent in these two areas in the cotton-growing season of 1980.