Generally, group A rotaviruses are the most common cause of paediatric diarrhoea. However, group B rotavirus, adult diarrhoea rotavirus (ADRV), was found to be involved in epidemics of severe gastroenteritis in several areas of China during 1982-1983 and had resulted in more than one million cases among adults as well as older children. Human group B rotavirus has been rarely reported outside China, but has been detected first from five adults with diarrhoea in Kolkata, India during 1997-1998 (strain CAL-1). During epidemiological studies at the National Institute of Virology (NIV) on hospitalized diarrhoea patients at Pune, India, faecal specimens from patients of >5 years age, which were negative for group A rotavirus by ELISA were tested by polyacrylamide gel electrophoresis (PAGE). We detected rotavirus RNA migration patterns similar to that of group B rotavirus in three faecal specimens from adults, two from the specimens collected in 1993 and one in 1998 from sporadic diarrhoea cases. RT-PCR was carried out using primers derived from gene 8 which codes for the NS2 protein, followed by nested PCR, which confirmed the presence of group B rotavirus in all three specimens. The sequences of the PCR products of NIV specimens were compared with that of CAL-1, ADRV and IDIR (infectious diarrhoea of infant rat) belonging to group B rotaviruses. The sequence analysis of the PCR products showed the highest identity with CAL-1, which was reported from Kolkata, India during 1997--1998. The finding suggests that human group B rotaviruses have been circulating in Pune. India, since 1993. This emerging virus may lead to more severe disease among adults in India. There is a need for surveillance of group B rotavirus infections, especially in adult diarrhoea cases and seroepidemiological studies on group B rotavirus are required among humans and animals of Western Maharashtra, India.