Globally rotavirus is the most common cause of severe gastroenteritis in children. From March 2005 through February 2007, a prospective hospital-based surveillance study was conducted at a national hospital in Phnom Penh, Cambodia, to estimate the burden of rotavirus hospitalizations among children aged <5 years old and to determine strain patterns. Children with diarrhoea underwent standard clinical evaluations. Parents were interviewed for demographic and family information. Faecal specimens were tested for rotavirus by enzyme immunoassay (EIA) and positive specimens were further characterized. Of 2817 hospitalized children with diarrhoea, 56% (n=1278) were positive for rotavirus antigen. The G1P[8] strain was the most common genotype (53%) followed by G2P[4] (10%). The findings suggest a need for improved prevention and control programs for rotavirus diarrhoea in Cambodia.