Introduction: The Sapporo-genogroup is one of the three major genogroups of human caliciviruses (HuCVs). Sapporo-genogroup HuCVs commonly cause acute gastroenteritis in children. Methods: We amplified by RT-PCR and cloned a 3.2 kb cDNA fragment from the 3′ end of the genome of a Sapporo-like HuCV in a diarrhea stool specimen from a child attending a child day care center (Houston/ DCC/90). The viral capsid gene was expressed by in vitro transcription/translation using the cloned cDNA.Results: Sequence analysis of the 3.2 kb cDNA showed that this virus has a genomic organization like the previous Houston/DCC/86 strain and the rabbit hemorrhage disease virus, in which the viral capsid protein is fused with the viral nonstructural genes. In vitro transcription and translation of the viral capsid gene revealed a major protein product of 60 K, that was immunoprecipitated by sera collected from two children infected with this strain. Houston/DCC/90 shares 82% amino acid sequence identity in the RNA-dependent RNA polymerase region, and 79% identity in the capsid gene with the Houston/DCC/86 strain. Houston/DCC/90 was not detected by an EIA using reagents specific for the prototype Sapporo/82 strain.Conclusions: Houston/DCC/90 is genetically related but distinct from the prototype Sapporo strain. This strain represents a new antigenic and genetic type in the Sapporo-like HuCV genogroup.