Simultaneous observations of times of occurrence of whistlers were made at Seattle, Washington, and Stanford, California, two hours every week from October 1951 to October 1952. Times were measured to an accuracy of about ±1 second. The objective was to determine the percentage of whistlers received at either station which were coincident at both.A total of 318 whistlers was received at Stanford and 283 at Seattle during simultaneous observations. The occurrence rate of whistlers (during a two‐hour period) varied from 0 to roughly 55 per hour at Stanford and from 0 to 70 per hour at Seattle. The correlation between the occurrence rates was poor.The number of true coincidences was found by subtracting the number of chance coincidences from the number of total coincidences. A method for computing the number of chance coincidences from a knowledge of the time intervals between whistlers at the one station was derived. The analysis showed that approximately 22 per cent were observed simultaneously at both stations.This result is examined in relation to possible theories of whistler origin and propagation, and is shown to support the Storey‐Eckersley th