A dendrogram showing the cluster analysis of the composite dataset of RFLP experiments using IS 1311 and IS 1245 as probes. A total of 98 isolates of Mycobacterium avium from Norway are included. The dendrogram was calculated by using the similarity by the average from experiments and the unweighted-pair group method using arithmetic averages clustering method. Correction for internal weights was used. Laboratory numbers, host and county origin of the isolates and the result of the PCR of ISMpa1 are given in columns on the right. The branch that includes the ISMpa1 positive isolates is marked with an asterisk. A total of 14 clusters (defined by 80% similarity) are grouped in rectangular frames and labelled A-N. Cluster N, including nine avian isolates and the reference strain R13, are represented by isolate 1247.