IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 10, October 2015. www.ijiset.com ISSN 2348 – 7968 Micronucleus test of Californian trout fish after treatment with the herbicide monosan for 48 and 96 hours Afrim Zeqiraj 1 , Shkelzen Elezaj 2 , Zafer Gashi 1 , Bujar Gruda 2 Medical laboratory ‘Biolab-Zafi-F’ Peje, Kosova 1 , Regional Hospital, Peje, Kosovo 2 Abstract: Aim: Fish are the object of study to detect potential contaminants, Mutagenic or carcinogenic present in the water. Besides fish toxicant similar response can provide higher vertebrates for chemicals that are carcinogenic to humans. Micronucleus test (MNT) is a technique developed by Schmid (1975), using the cells as an object of study, and by treating with chemicals as a genotoxic test. Micronucleus test can be used to fish, frogs and birds, and is a biological warning direct or indirect contamination of aquatic environment in vivo. Research goal: The purpose of this research was verified genotoxic effect of herbicide monosan in peripheral blood erythrocytes of trout fish of California (Oncorhynchus mykiss), thus to prove damage to the genetic material (chromosomes) in erythrocytes by MN test. Results: It’s seen that the frequency of micronucleus (MN) in erythrocytes of fish treated for 96 hours in all concentrations ( 0.2, 0.3, 0.4 and 0.5 ml / L), is in scale significantly higher (p <0.001) compared with the control group of fish. The high frequency with micronucleus in significant degree is also determined to fish treated for 48 hours in all dilutions (0.2, 0.3, 0.4 and 0.5 ml / L) compared with the control group. Conclusion: In our research we found a significant increase (p <0.001) the frequency of MN in peripheral blood erythrocytes of fish treated with herbicide monosan, compared with control group of fish. Key words: Micronucleus test, herbicide monosan, Californian trout fish. Introduction A micronucleus test is a test used in toxicological screening for potential genotoxic compounds. The assay is now recognized as one of the most successful and reliable 523