An investigation of the impact of El Niņo/Southern Oscillation (ENSO) on North American (NA) snow cover was carried out using NOAA satellite data for the post-1971 period, and historical station data for a much longer 1915 to 1992 period. El Niņo and La Niņa snow cover composites were formed from the major events occurring in each time period following Groisman et al. (1994). For the satellite data, the compositing was based on five prominent El Niņo and three prominent La Niņa events. For the longer period of station data, 10-year composites of prominent events were able to be formed to give a more robust estimate of the average influence of tropical Pacific SST anomalies on NA snow cover. Comparison of the two sets of results revealed important differences particularly with respect to La Niņa. The satellite La Niņa composite showed major reductions in winter snow cover over the southern U.S. while the station data revealed a relatively weak La Niņa influence on snow cover, with a tendency for increased snow cover in all months. The El Niņo composites showed some regional similarities, especially reduced spring snow cover over western portions of the continent. Analysis of the significance of composite anomalies revealed that El Niņo was associated with locally significant reductions in snow cover over western regions of the U.S. and Canada from December to April. La Niņa was found to be associated with significant increases in winter snow depth over southern B.C. and the Prairies from January to April. In terms of NA snow cover extent (SE), the 10-year station data composite results revealed that El Niņo was associated with significant reductions of SE in December. It is hypothesized that the enhanced December sensitivity of snow cover to El Niņo conditions is related to a coincidence of the El Niņo air temperature anomaly with the snow cover-temperature sensitive zone which is in its most westward position during December.