A large outbreak of aseptic meningitis occurred from April to November 2001 in Taiwan. Of the 1,130 enterovirus-infected patients, echovirus 30 (E30) infection was diagnosed in 188 (16.6%), with the patients having various clinical manifestations including aseptic meningitis (73.9%), young infant fever (6.9%), respiratory symptoms or herpangina (13.3%), or others (5.9%). The majority of the E30-infected patients were between 3 and 10 years old. Of the 264 E30 strains identified, 94.3, 71, and 67.4% were isolated from RD, MRC-5, and A549 cells, respectively. Primary isolation of E30 required mean times of 3.7 days for RD cells and 4.1 days for MRC-5 and A549 cells. Among all E30-positive patients, virus was most frequently isolated from throat swab specimens (85.2%) and, to a lesser extent, stool (76.4%) or cerebrospinal fluid (70.1%) specimens. The virus isolates were initially identified as echovirus 4 (E4) on the basis of immunofluorescence staining with anti-E4 and anti-E30 (Bastianni prototype) monoclonal antibodies. However, upon performance of the neutralization test, E30-specific reverse transcription-PCR, and sequencing of the VP1 gene, the results identified these isolates as E30, not E4, indicating that the reagent used to type E30, which is produced with the Bastianni strain as the immunogen, is inadequate for the identification of recent E30 isolates in Taiwan. Phylogenetic analyses of the VP1 genes of these isolates showed that their sequences differed from those of E30 isolates from the GenBank database by 9.1 to 25.2%, suggesting that this outbreak was caused by a new variant strain of E30 introduced into Taiwan in 2000 that resulted in the widespread aseptic meningitis epidemic in 2001.