Objective: Lactobacilli are the most commonly used probiotics. We examined the influence of cell-free supernatants (CFSs) of Lactobacillus acidophilus (La), L. fermentum (Lf), L. plantarum (Lp) and L. rhamnosus (Lr) on growth, adhesion and invasion of C. jejuni 81116 and RM1221 in human adenocarcinoma colon cells (HT-29). We also analyzed the influences of CFSs, C. jejuni and their combinations on HT-29 cell viability.Materials and Methods: Growth and adhesive-invasive bacteria counts were determined using the spectrophotometric method and colony counting method, respectively. We used methyl thiazolyl diphenyl-tetrazolium bromide (MTT) assay for detection of HT-29 cell viability.