A “worst case” of scintillation activity is presented by the analysis of data of a period of severe magnetic activity, August 3–10, 1972. The effect of the dense ionospheric irregularities produced by these storms on scintillation at high latitudes is viewed as a function of local time and the invariant latitude of the propagation path, as well as magnetic activity. Storm period data taken at high, middle, and equatorial latitudes are analyzed and compared with the seasonal means. In the high-latitude irregularity region, dramatic increases of scintillation index at 254 MHz were noted. Cumulative amplitude probability distribution functions are given for the high-latitude data with the aim of giving to systems designers signal statistical data for “worst case” conditions. Middle-latitude stations show little reaction to the magnetic activity. At equatorial latitudes during July and August, the longitude of the observatory determines the reaction. Accra (Ghana) data show a slight decrease in scintillations during the August storms. At Huancayo (Peru) scintillations increase in the postmidnight period.