An analysis of the onset and spatial extent of discontinuities in the late 1960's in different atmospheric data products is performed. Discontinuities are found in both the NCEP/NCAR and ERA-40 reanalyses in various surface variables including sea level pressure (SLP) in both data sets over Africa, in the NCEP/NCAR reanalysis also over Asia and in the ERA-40 reanalysis also over South America, and precipitation in the NCEP/NCAR reanalysis over North Africa. Discontinuities are also found in 2 m air temperature in both reanalyses. The discontinuities in SLP extend into the lower troposphere. The main cause of these discontinuities appears to be missing or limited synoptic data prior to the late 1960's.