Biological agents have transformed the management of inflammatory and proliferative disorders. Safety issues have been raised, particularly the increased risk of opportunistic infections and secondary cancers. We report four cases of melanoma worsening or occurring after rituximab treatment for associated B-cell lymphoma, and discuss the accountability of the molecule in this process. In three cases, melanoma was diagnosed before or at the same time as a B-cell lymphoma treated with rituximab associated with chemotherapy and we observed rapid metastatic progression. In the last case, melanoma appeared after 5 years treatment with rituximab for a follicular lymphoma. Although it is premature to conclude on the role of rituximab in melanoma, careful follow-up and registration of such cases are important to gain further insight on this topic.