The aim of this study was to assess the effect of commercial aurintricarboxylic acid (ATA) against Cryptosporidium parvum. The anticryptosporidial effect of ATA was evaluated in two in vitro models and in vivo in experimentally infected neonatal mice. Inboth in vitro models, ATA completely inhibited sporozoites. The treatment of neonatal mice with a daily ATA dose led to 97-99 % inhibition of infection without any observable negative effects on the animals. In comparison, the mean reduction of infection for paromomycin used as a positive control was 79-84 %. It can be concluded, ATA exerted high anticryptosporidial activity and should be considered for further study.