Smoking has an impact on the development and outcome of rheumatoid arthritis (RA) and lupus. In RA, smoking is associated with the development of the anti-cyclic citrullinated peptide (CCP2)-positive subset. This risk is increased in heavy smokers carrying at least one copy of the HLA DRB1 shared epitope (SE) alleles. Whereas this interaction between smoking and SE relevant in northern Europe, discrepant results have been observed in other geographic locations, suggesting the involvement of other environmental stimuli and/or gene polymorphisms. There is no interaction between tobacco exposure and PTPN22 1858T for the development of anti-CCP-positive or anti-CCP-negative RA. A strong association exists between smoking and the occurrence of extra-articular manifestations (subcutaneous nodules and cardiovascular events), but smoking has no influence on radiographic outcome. In lupus, tobacco exposure has an impact on the production of anti-double-stranded Desoxyribonuclic (dsDNA) and possibly on the development of the disease, as well as on disease activity/severity. In both diseases, smoking might interfere with drug efficacy.