New virus structures continue to be determined. These often exhibit novel features but most use at least one 'jellyroll' motif in their capsid proteins. I discuss why this might be. Studies on influenza virus proteins now provide us with detailed information on the interaction of the outer coat proteins with sialic acid, the viral receptor. The determination of the structure of HIV reverse transcriptase, revealing a structurally asymmetric heterodimer, represents a major breakthrough. © 1993 Current Biology Ltd.