Computer programs have been built for automatic collection of all intensively monitored physiological data, their storage and retrieval, graphically browsing the data, and testing any processing methods. A robust method for performing symbolization is proposed and tested with real data using the programs mentioned above. The method for performing symbolization is based on the use of a median filter bank for extraction of activities within speed of variation ranges. These are used to characterize the signal contents in terms of variability to extract information about short-term activity and long-term trends. The symbolic description of the signal at a given moment is based on this information. The authors' method also gives information about the credibility of the activity findings and their symbolic representation.<<ETX>>