1987/88 (Lin 1989). In India, larval mortalities in hatcheries due to MBV have been recorded by Ramasamy et al. (1995), and similar catastrophic mortalities have been recorded in Malaysia (Nash et al. 1988) and Thailand (Thikiew 1990). Simultaneous occurrence of MBV with WSSV in apparently healthy P. monodon PL in India was found by Otta et al. (2003). Recently, WSSV has emerged as one of the most serious disease problems in cultured shrimp populations all over the world. It affects all of the most important commercial species of penaeid shrimp (Lightner 1996). Wild marine shrimp and many cultured and captured crustaceans have also been found to harbor this virus (Hossain et al. 2001, Chakraborty et al. 2002). The presence of WSSV in Penaeus monodon PL in India was reported by Otta et al. (1999). Although simultaneous detection of WSSV and MBV in apparently healthy P. monodon PL was reported by Otta et al. (2003), there is no report on the presence of HPV in healthy larvae. In this context, the present study was carried out to screen for all 3 aforementioned viruses by PCR, both in samples of hatchery-reared PL collected by us, and in samples submitted by farmers.