A reverse transcription (RT) and polymerase chain reaction (PCR) was designed for the detection of astroviruses based on a conserved nucleotide sequence in the 3'-end of the genome of the 7 known serotypes of human astrovirus. Thirty-eight samples found to contain astrovirus by electron microscopy (EM) were used for evaluation of the assay. The samples were dialyzed for 1 h to remove potential low molecular weight inhibitors of the RT-PCR. Immediately before RT, 1 microliters of the samples were incubated at 94 degrees C for 2 min to disrupt the viral particles. Thirty-six of the samples were positive by PCR, including samples of all 7 serotypes. The two samples that were negative, could hve been false positive by EM, or the viral RNA could have been degraded. All other viruses examined, including calici-, rota- and enteroviruses, were negative.