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X-ray sources detected in archival PSPC images. Each source was tested for time variability using a Kolmogorov Smirnov method which allowed us to find several hundred rapidly variable objects. Among the already identified variable sources the majority are flare stars, but X-ray transients and a number of AGN have also been found. About 1800 entries in the WGA catalog also appear in the list of Einstein IPC sources. These have been tested for long term ($ \simgt 10$ years) variability. Most types of objects exhibit large amplitude variations on this time scale with late type stars showing the widest range of variability. Within the class of AGN preliminary results indicate that the amplitude of variability decreases with redshift and that there is no obvious correlation with luminosity.
