Aims: To develop a method for assessing the relative epidemiological significance of possible infection sources for human campylobacteriosis. Methods and Results: Using fluorescent amplified fragment length polymorphism (AFLP), 243 apparently epidemiologically unrelated Campylobacter jejuni isolates were genotyped (77 human, 46 cattle, 49 pet and 71 poultry isolates). In total 136 different phena were identified, of which 48 were clusters grouping at least two isolates. Isolates from different sources were frequently clustered together, underlining the high degree of source mixing and the lack of host specificity of C. jejuni. The phena were classified into different phenon types according to the sources of the isolates they contained. The occurrence of these phenon types was analysed using an area-proportional Euler diagram to describe epidemiological relatedness among C. jejuni isolates. Group separation statistics revealed that 43% of analysed human isolates expressed maximum similarity to other human isolates, 9% to cattle isolates, 21% to pet isolates and 27% to poultry isolates; these results were in accordance with the pattern observed in the phenon cluster analysis. Conclusions: Based on the grouping of strains into molecular similarity clusters, ecological patterns between sources can be investigated. Significance and Impact of the Study: This approach is a new methodological contribution to establish the relative epidemiological significance of concurrent infection sources.