in many countries, the enterovirus 71 (ev-71) picornaviridae family is associated to hand, foot and mouth disease in addition to acute neurological diseases while in brazil these viruses are more closely associated to the latter group. the aim of this research was to use the first ev-71 isolate of the northern region of brazil in molecular and seroepidemiologic studies. two (2.2%) out of 88 stool samples (44 cases of afp), collected from january 1998 to december 2000 were positive for ev-71 isolation (73442/pa/99). nucleotide sequence of the gen that codifies the vp1 protein showed that isolate 73442/pa/99 was similar to the ev-71 strains belonging to genotype b - more closely identified with ev-71 from north america. neutralization test with 389 sera samples collected from january 1998 to november 2001, from individuals ranging from 0 to 15 years of age living in the city of belém, state of pará showed the following results in relation to isolate 73442/pa/99 and prototype brcr: a total of 207 individuals (53.2%) had neutralization antibodies to both viruses, 167 (42.9%) had no antibodies and 15 showed the presence of neutralizing antibodies to one of the two viruses. only 20.2% of the children aged 0 to 3 had neutralizing antibodies to ev-71, indicating that these children were more susceptible to the infection. both the seroprevalence study and vp1 sequencing were important to demonstrate the spread and the molecular pattern of the ev-71 circulating in the northern region of brazil.