Adeno-associated virus (AAV), capable of producing significant, long-term transgene expression, is one of the least toxic vectors employed in pre-clinical and clinical studies of gene transfer. One limitation is generation of neutralizing antibodies against viral capsids, blocking gene expression after readministration. AAV2 capsids were modified with poly(ethylene) glycols (PEGs) activated by cyanuric chloride (CCPEG), succinimidyl succinate (SSPEG) and tresyl chloride (TMPEG). SSPEG and TMPEG conjugation did not compromise gene transfer to the liver and muscle and improved gene expression in the lung 5 fold. Transduction efficiency of CCPEG-AAV was impeded in all tissues by aggregation. TMPEG afforded the best protection from neutralization in vitro and in vivo. Gene expression in mice immunized against unmodified AAV was reduced by a factor of 10 from that of naïve animals after intramuscular rechallenge with PEGylated AAV but was not significantly different from naïve mice after intravenous readministration (p=0.08). Gene expression was markedly reduced in muscle after two doses of PEGylated AAV. In contrast, mice given two intravenous doses of TMPEG-AAV had significantly higher transgene levels than naïve animals 14 days after rechallenge (p=0.001). This technology could promote successful readministration of vector in the clinic and marked expression in patients with anti-AAV antibodies.