Effects of protease, $CaCl_2$ EGTA, polybrene, medium pH, and formaldehyde on the infection and inactivation of human rotavirus Wa were investigated using T-flask culture of monkey kidney MA-104 cells. Rotavirus titer was improved by the addition of trypsin or clostripain. Rotavirus titer was increaeed 8 and 10 time sin the infection medium supplemented with 300 $mu extrm{g}$/mL of $CaCl_2$ and in the medium adjusted its pH to 8, respectively. However, addition of EGTA or polybrene to the medium decreased rotavirus titer. Rotavirus titer was reduced to 53-95% of the initial value at 1 hr after formaldehyde treatment. Furthermore, rotavirus was inactivated more than 98% at 12 hrs after formaldehyde treatment.