Campylobacter jejuni growing in liquid culture was found to exhibit gross morphological changes with time. Exponentially growing cells showed typical short spiral forms. At mid-stationary phase the cells became approximately twice the length of the exponential forms. Late stationary/early decline phase cells were seen to be a mixture of coccal forms and cells which were between 3 and 4 times the length of exponentially growing cells. Continued incubation of cultures eventually resulted in a population largely of coccal forms. These morphological changes have not previously been observed when Camp. jejuni has been grown on agar-based solid medium. It is likely that such changes result from the differential expression of genes that control the timing of cell division.