AbstractIn 1986 a chemical spill took place from the Sandoz plant in Basel, Switzerland, into the Rhine River. Several chemicals entered the river and were transported downstream. In this paper we rank the environmental hazard of eight chemicals, Disulfoton, Dinitroorthocresol, Propetamphos, Thiometon, Parathion, Etrimphos, Metoxuron and Fenitrothion found in the German section of the Rhine River. Five attributes related to the toxicity, physio‐chemical characteristics and fate are used to rank the chemicals. The fate attributes were derived using the fate model EXWAT. Two ranking methods were used and results were compared. One method is based on the standardization of the data into attributes and aggregation into an index. The second method allows one to visually compare chemicals based on a large number of test results which might otherwise be very confusing when displayed in a table form: The Hasse diagram is an effective graphical display of data difficult to understand otherwise. Results by both ranking methods show that these chemicals can be divided into two groups, the most hazardous include Dinitroorthocresol, Propetamphos and Parathion, and the least hazardous include Disulfoton, Thiometon, Etrimphos, Metoxuron and Fenitrothio