The Allium test, using *Allium cepa* (onion), is proposed as a standard method for environmental monitoring. This test is characterized by its low cost, ease of handling, and good chromosome conditions, making it suitable for studying chromosome damage and cell division disturbances, including aneuploidy risk evaluation. The ability of root cells to activate promutagens (the MFO-system) further enhances its applicability. The test involves growing onions in various concentrations of test chemicals, allowing statistical analysis and the determination of Effect-Concentration values from growth curves. Positive results in the Allium test should be considered a warning of potential health and environmental risks. The test has been validated through various applications, including the testing of known and unknown chemicals, and has shown good correlation with other test systems. The Allium test is particularly useful for screening complex mixtures and can be used as part of a test battery in environmental monitoring.The Allium test, using *Allium cepa* (onion), is proposed as a standard method for environmental monitoring. This test is characterized by its low cost, ease of handling, and good chromosome conditions, making it suitable for studying chromosome damage and cell division disturbances, including aneuploidy risk evaluation. The ability of root cells to activate promutagens (the MFO-system) further enhances its applicability. The test involves growing onions in various concentrations of test chemicals, allowing statistical analysis and the determination of Effect-Concentration values from growth curves. Positive results in the Allium test should be considered a warning of potential health and environmental risks. The test has been validated through various applications, including the testing of known and unknown chemicals, and has shown good correlation with other test systems. The Allium test is particularly useful for screening complex mixtures and can be used as part of a test battery in environmental monitoring.