Abstract: We have earlier reported on the expression of Sendai virus HN gene in BHK-21 cells (Ansari and McQueen 1999). As expression gives no idea about the functional activity of the protein therefore we are reporting here on the functional activities of the expressed HN protein. HN is a multi functional molecule having hemagglutinin activity and neuraminidase activity. We tested both the activities separately and found both the activities in the in vitro expressed HN protein. The results confirmed that the HN gene not only is synthesized but is functionally active too.