Midlatitude cyclones are one of the primary mechanisms for the poleward transport of heat and are therefore important components in the global energy balance. Tropical cyclones are similarly important in the vertical distribution of mass and energy. The midlatitude cyclone has been extensively studied on regional scales, but climatological information on the global scale is decades old. Recent studies have dealt with surface and 500 mb cyclones for areas as small as the western U.S. and as large as North America. In this study we use the 40 year NCEP/NCAR reanalysis dataset to develop a global climatology of 500 mb and 1000 mb cyclones for the period 1958 - 1997. Trends in cyclone frequencies and deepening rates are determined, as are differences between El Nino and La Nina years. Results indicate that cyclone frequencies in the Northern Hemisphere midlatitudes have steadily increased, as have tropical cyclone numbers in both hemispheres. Other areas have shown no trend or slight downward trends (decreasing frequencies), and even opposite trends at the two vertical levels. El Nino and La Nina year frequencies are clearly different, with greater numbers of midlatitude cyclones during El Nino years in the Northern Hemisphere.