Pigeon herpes encephalomyelitis virus (PHEV) was stable at -70 C for at least 4 months. When stored at -20 C, the virus lost 80% of its infective titers in 4 months. When stored at -10 C, however, the titers decreased rapidly; no detectable virus remained within 12 weeks. PHEV was thermolabile: it was completely inactivated at 56 and 60 C for 10 and 2 min respectively. It was also killed by 1% cresol and 2% sodium hydroxide for two hr and 2% septol for 24 hr. Two-percent phenol or formaline for 2 hr, however, significantly decreased virus infective titers. Phenol-purified DNA extracted from PHEV showed an ultraviolet spectrum of typical nucleic acids that had ratios of absorbancies at 265 nm/280 nm between 2 and 2.3. The extracted viral DNA was infectious in chorioallantoic membrane and chick embryo fibroblast cell cultures, but it was not noninfectious when given to pigeons. DNA infectivity was destroyed by DNAse but not RNAse treatment. Extracted DNA was not neutralized by antiserum against the intact virus, and it lost its infectivity property when heated at 70 C for 10 min.