SummaryEight monoclonal antibodies (MAbs) were tested for the use in immunogold staining of Sindbis virus (SIN) antigen in cultured Baby Hamster kidney (BHK) cells. The antibodies were directed against the capsid (C) protein (5) or against the glycoprotein E1 (3), respectively. Four out of five anti‐C MAbs and two out of three anti‐E1 Mabs reacted on frozen sections, whereas two of the anti‐C antibodies and none of the anti‐E1 antibodies reacted on Lowicryl K4M‐emedded cells. The MAbs reacting, in particular the anti‐C Mabs which react on Lowicryl K4M‐sections, will allow further studies of the pathogenesis and replication of alphaviruses on the cellular level. The results also confirm the conformation‐dependence of the glycop