The early extra- and intra-cellular interaction between adenovirus type 2 and HeLa cells was studied in the presence of benzyl alcohol as a fluidizing agent. The process of virus attachment and internalization were not affected at 5-15 mM of benzyl alcohol at 25 degrees C. Under the same conditions an enhancement by 45% at the most was demonstrated for the cell-mediated virion uncoating. By completely blocking virion internalization with 50 mM azide the uncoating was reduced to 20% of the normal level. The remaining surface-located uncoating was not affected by benzyl alcohol. It was demonstrated that an enhancement of the intracellular virion uncoating was followed by a raised production of the hexon antigen, which was interpreted as an increase in the specific infectivity of the virus.