States that since 1980, UKOLN has been carrying out a survey to monitor the availability of bibliographic records in the BNB files on the British Library automated information service (Blaise). Work on the ordering stage sample is now to be extended by investigating the availability of records from other sources of bibliographic records. Looks at the survey and the new sources to be included in the extended survey. Divides the participant sources (BNB, BDS, Book Data, J. Whitaker & Sons, BLCMP, CURL, LASER, OCLC and SLS (Information Systems) Ltd into two groups and describes the survey methodology and sample structure. Presents a set of source profiles which have been prepared as background material to accompany the results for each source since straight comparisons would not be advisable, given the differences in objectives and set-up of the sources. Gives some comparisons of the features of different sources.