Hatchability of fertile eggs incubated with their small ends up (SEU) was 16 to 27% lower than for eggs set with their large ends up (LEU). In addition, the SEU position produced more nonviable chicks. 2. There were no differences in post-hatching performance between the two incubation treatments. 3. A survey in a commercial hatchery revealed that the frequencies of eggs set upside down by mistake varied from 0.3% to 3.4%. The setting of eggs upside down was attributed not to difficulties in distinguishing the large and small ends of the eggs but to human error. A decrease in the number of Grade-A chicks of about 0.2% was observed for every 1% of eggs set upside down, suggesting it may be of economic importance to ensure that the eggs are set properly with their large ends up.
