This thesis is an investigation of human campylobacteriosis and Campylobacter from retail chicken in two Ontario health units. The objectives were to investigate the symptoms, severity, antimicrobial use (AMU), antimicrobial resistance (AMR), and duration of illness (DI) in clinical campylobacteriosis, the prevalence and AMR of Campylobacter from contaminated retail chicken, and the relationship between clinical and chicken Campylobacter isolates based on Comparative Genomic Fingerprinting (CGF). In the participating health units, campylobacteriosis case data were collected and retail chicken was sampled from randomly selected stores. Campylobacter isolates from clinical cases and chicken were antimicrobial susceptibility tested and CGF typed. A Cox proportional hazard model was used to investigate the DI in campylobacteriosis. Logistic regression models were used to explore the relationship between clinical and chicken CGF types. Of 250 cases, 52% reported taking antimicrobials for their campylobacteriosis. In 124 cases with accompanying isolate and AMR information, 6 (4.8%) and 2 (1.6%) isolates were resistant to ciprofloxacin and erythromycin, respectively. In 749 chicken isolates, 14 (1.9%) and 25 (3.3%) isolates were resistant to ciprofloxacin and erythromycin, respectively. No isolates were resistant to both antimicrobials. While the low prevalence of AMR to ciprofloxacin and erythromycin was encouraging, the high proportion of cases treated with antimicrobials was concerning and efforts should be made to reduce unnecessary treatment. The Cox model identified that use of a macrolide for less than the recommended duration, use of ciprofloxacin for the recommended duration, and use of other antimicrobials, were factors associated with decreased DI. The impact of AMU was consistent regardless of when in the course of illness it began. The CGF results were available from 115 clinical and 718 chicken isolates. A Campylobacter CGF reference database was used to identify CGF types that comprised at least 80% of isolates from chicken, based on 90% fingerprint similarity (CA90). Isolates from urban cases were significantly more likely than rural cases to be CA90. In Canada, the majority of campylobacteriosis cases are urban dwellers. Therefore, the association between urban cases and CA90 emphasizes the importance of Campylobacter from retail chicken on public health.