In the present work an attempt has been made to study the changes in certain haematological indices following Cythion (an organophosphate pesticide) treatment in a teleostean fresh water air breathing murrel fish，Channa gachua (Ham) which are also cultured in paddy fields. The treatment of Cythion caused anaemia i.e. significant decrease in RBC counts, Hb content and PCV values. However, a clear trend of increase in WBC counts，MCV and MCH was observed. MCHC values did not differ much orto a significant level. The details have been discussed in this paper.