OBJECTIVE To determine the extra-lengh of stay and the economic loss for nosocomial infections of group A rotavirus in children′s hospital. METHODS We performed a 1∶1 case-control study to determine the cost of nosocomial rotavirus infection. Data of hospitalized cases were collected from Jan 1 2007 to Dec 31 2007. RESULTS The average medical expenses in case and control group were 7589 yuan and 5319 yuan,the average increased cost per case was 2269 yuan,the expenses for medicine,treatment,laboratory test and bed accounted for 47.42%,19.96%,17.10% and 9.03%,respectively (P