Rotaviruses can be detected easily, and methods have been developed to visualise their characteristic morphology, to detect rotavirus proteins through immunological methods or the virus genome, either directly by polyacrylamide gel electrophoresis or after reverse transcription of the viral RNA and amplification by PCR. The abundance of virus particles found in clinical samples during an acute infection makes the detection of rotavirus proteins, mainly VP6, the method of choice for virus detection. Molecular methods are generally reserved for the characterisation of a diverse population of viruses circulating in many mammalian species. Characterisation methods have been developed to determine diversity within genes encoding viral structural proteins, VP4, VP7, and VP6 and the non-structural protein and viral enterotoxin, NSP4. The combined use of the detection and characterisation methods described in this chapter allows novel rotavirus strains resulting from genetic reassortment among common strains, reassortment among animal and human strains and zoonotic strains to be identified. Also, strains in which diversity is generated through the accumulation of point mutations during virus replication are identified. The development of safe and effective rotavirus vaccines necessitates the detection and characterisation of rotaviruses of genomic and antigenic diversity circulating in both the human and animal populations.