A study was made of the serial holding statements in PHILSOM over a six-month period, in order to determine the desirability of printing the complete serial holding statements monthly. Attention was given to the frequency of internal and update changes in both active and dead entries. The results indicate that while sufficient activity is observed in active serial entries to warrant their monthly updating, dead serial entries remain constant over this period. This indicates that a large group of PHILSOM entries can be easily identified and isolated, facilitating division and independent updating of the resultant lists. The desirability of such a division, however, must also take into consideration the user's ease in handling such a segmented listing.