The Unregulated Contaminant Monitoring Rule (UCMR) requires all water systems serving more than 10,000 people and a representative subset of the less than 10,000 systems to monitor for a specific set of compounds that may be regulated in the future and to enter the resulting data and associated QC into a national contaminant occurrence database (NCOD). Early experience with the UCMR suggests that although some of the difficulties that were inherent in the Information Collection Rule (ICR) have been overcome, there are still a lot of hurdles that must be passed to ensure success. Having laboratories enter results and QC directly into the database eliminates a major source of errors, but because labs are still highly dependent on utilities to provide sample identifications that are consistent with the NCOD in order to successfully enter the data, it is apparent that excellent communications between the labs and the utilities will be necessary. Additionally some of the QC requirements of the UCMR present challenges to labs and utilities alike. This paper describes some of the potential problem areas and suggests ways to overcome them, based on direct experience and a comparison with the ICR. Includes 3 references, tables.