Alternative assessment is a central procedural step in environmental law, designed to compare different means of achieving regulatory objectives while integrating information on environmental impacts into decision-making. Despite its potential to enhance transparency and legal quality, it often conflicts with demands for faster procedures. This study provides a comprehensive and systematic account of alternative assessment within European and German environmental law. It covers diverse legal areas, including environmental and strategic impact assessments, habitat protection, nature conservation, chemical and plant protection law, water law, and pollution control. Based on the constitutional and EU-law framework, the author classifies alternative assessments according to actors, functions, and legal character. The analysis explores the procedural and substantive implications of these classifications, particularly regarding implementation, error consequences, and legal remedies. The work further engages with issues of legal development, discussing potential reforms such as the introduction or abolition of assessment duties, the reconciliation of environmental protection and procedural acceleration, and future research needs. It thereby offers a rigorous and forward-looking contribution to the theory and practice of environmental procedure law.