Aerotolerance of Campylobacter jejuni ATCC 29428 and one of its aerotolerant mutants (strain MC711-01) was measured at 37°C and 42°C. The aerotolerance of C. jejuni was higher at 42°C than at 37°C. Three different lots of Gibco dehydrated Brucella broth were used to prepare Brucella agar. The agar media were then tested to see if they differed in their ability to support growth of C. jejuni. However, only slight differences in viable counts of C. jejuni were obtained between lots. Ageing of dehydrated Brucella medium for 2½ months and hydrated Brucella medium for 1½ months greatly affected the growth of C. jejuni and decreased its aerotolerance. This is probably due to the deterioration of the sodium bisulfite in Brucella medium during storage, because addition of 0.01% sodium bisulfite (the same amount as contained in the Brucella medium) to the aged medium (dehydrated or hydrated form) restored the ability of the medium to support growth of C. jejuni under various O₂ levels equivalent to or even better than that obtained with fresh Brucella medium. Moreover, when Brucella agar was prepared from the individual chemical and peptone components, only the medium containing the 0.01% bisulfite yielded colony counts of C. jejuni similar to that obtained on fresh commercial Brucella medium. When sodium bisulfite was omitted, viable counts and aerotolerance were decreased. / Master of Science