The evidence base of internet-based self-help interventions has been rapidly growing for mental health conditions over the past decade. However, to date a systematic review of the application of this technology to chronic health conditions has not been reported. The objective of the present review was to therefore critically appraise the research on the efficacy of internet self-help interventions for distress and disease outcomes in adults with physical health complaints. Electronic searches were conducted in Embase, CINAHL, MEDLINE and PsychINFO, and reference lists were examined. Twenty four studies met inclusion criteria, covering 8 health conditions. Across health conditions, consistent evidence was obtained that online therapeutic interventions were efficacious in improving disease-symptoms and control, with the exception of diabetes. Mixed evidence was obtained for distress outcomes: 3 health conditions demonstrated consistent benefit (irritable bowel syndrome, tinnitus, and one heterogeneous chronic illness population); one condition obtained moderate support (chronic pain); while results were not promising for diabetes. The limited research conducted among epilepsy, cancer, and chronic fatigue precluded conclusions from being drawn. Few studies met all methodological quality criteria. This review demonstrates that internet-based self-help interventions hold guarded promise in the amelioration of distress and disease-control, and further research implications are discussed.