The measures needed for the protection of the Earths ozone layer are decided regularly by the Parties to the Montreal Protocol, now consisting of 184 countries. The Parties are advised on knowledge relevant to this task by three panels of experts: the Scientific, Environmental Effects, and Technology and Economic Assessment Panels. These panels produce an assessment everyu four years; the latest environmental effects assessment was published in Photochem.Photobiol.Sci., 2003, 2, 1-72. In the intermediate years the panels keep the Parties informed on new developments. The following Progress Report is the 2003 update by the Environmental Effects Assessment Panel. Since the first assessments in 1989, the complexity of the linkages between ozone depletion, UV-B radiation and climate change has become more apparent. This makes it even clearer than before that we are dealing with long-term developments, which can be complicated by large year to year variabilities.