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Stowaway transport rates were obtained from behavioral observations of 14 house mice (Mus domesticus) and 14 deermice (Peromyscus maniculatus) during commercial transport. One house mouse escaped during unloading and flaking of 2,500 kg 2-year old oat hay. Three house mice and two deermice were hand-caught on trucks during unloading of 51,110 kg transported barley straw and grass hay. One house mouse was hand-caught after being buried alive in grain. Two house mice escaped during unloading of a semitruck holding dog food. House mice (one live, six recently-dead) and deermice (two recently-dead) were taken from a feedmill screen over which had passed 940,313 kg grain. Ten deermice were trapped in a pickup truck cab. In conclusion, multiplying these transport rates, (7(10"s) house mice per transported kg hay and 7(1O6) house mice per transported kg grain, by the worldwide volume of transported hay and grain implies thousands of stowaway house mice occur. Deermice have comparable transport rates. Experiments (N=82) were done to determine if a particular sex or age predominates among stowaways. For each experiment, I put one to five hand-caught or trapped house mice in a haybale, let them remain in the haybale for 1 to 13 days, put the haybale in a wheelbarrow, pushed the wheelbarrow for 15 minutes, and then searched for transported mice. Stowaways, mice remaining during transport, included 74 of 115 mice (64 %), which were primarily lower weight classes, characterizing house mice coming into reproduction. In conclusion, live stowaways should arrive in > 50 % infested loads.