The information of the toxicological and ecotoxicological properties of co-formulants –non-active ingredients in formulated products- are often very sparse. This report shows that search in databases and otherwise in the open literature is of importance, which enhances the knowledge of both adverse and less severe effects of the co-formulants. A joint effort was made to map the occurrence of co-formulants used in the Nordic countries, the volume used and number of products they were manufactured in. This resulted in a list of more than 600 compounds, based on data from Sweden, Denmark and Norway. Compounds with sufficient data and of toxicological and/or ecotoxicological concern were selected in a Negative list. Co-formulants that from different sources and experience could be regarded as of minor concern were not further investigated. Of the remaining compounds, those suspected to have the most adverse properties were selected for further investigation. Efforts were made to fill the data gaps by rather comprehensive literature surveys. QSAR predictions were also performed for most of these compounds