Transposon mutagenesis was used to introduce specific mutations in the chromosome of Bordetella avium. The transposon Tn5 was transferred by conjugation to B avium from Escherichia coli strain SM10 by the suicide plasmid vector pSUP1011. A defined minimal medium for growth of B avium was developed for scoring transposon-containing mutants for specific nutritional requirements. Approximately 1% of all mutants tested were auxotrophic in some form, and these organisms were grouped into 13 classes. Also, 2 classes of hemagglutination-negative mutants were isolated. Stability of Tn5 insertion was examined, and frequencies of reversion less than 10(-7) were observed, indicating stable mutations.