Purpose: To test whether CP49 and filensin represent a new class of intermediate filament (IF) proteins by determining their intron positions. Amino acid sequence data has shown that CP49 and filensin are homologous to other IF proteins but the overall percentage amino acid identity of these proteins is low when compared to other IF proteins. The intron positions are highly conserved within each class of IF protein and therefore the identification of the intron positions in CP49 and filensin would establish whether these proteins represent a new class of IF protein or if they should be included in existing groups (type I-V). The classification of new IF proteins such as CP49 and filensin will contribute to our understanding of the evolutionary origins of intermediate filament proteins.Methods: Using CP49 and filensin intron sequences, specific primers were used to isolate P1 clones. The P1 phage system was used as large fragments (85-100kb) of genomic DNA can be cloned which will include the complete gene of interest. The P1 clones were sequenced to identify intron positions.Results: the initial positional intron analysis has shown that CP49 and filensin can both be classified into the existing IF groups.Conclusion: CP49 and filensin do not represent a new class of IF proteins and have evolved from a common ancestral gene. The isolation of the P1 clones has not only allowed investigation of the gene structure but will also enable examination of the regulatory sequences for these genes.