1. This paper is a report of biological agents that contaminate Greater Rhea (Rhea americana) eggs during artificial incubation. 2. The cleanliness of eggs when collected, and the period of storage prior to incubation, were investigated to assess their effects on microbial contamination and hatchability. 3. A total of 14 bacteria and 4 fungi species were isolated within the egg in the laboratory. 4. Microbial contamination was higher (24%) in very dirty eggs than in eggs which were clean or dirty (16%). Hatching success was lower (30%) for very dirty eggs, compared with 42% for clean or dirty eggs. 5. The percentage of microbial contamination of stored eggs (10%) did not differ significantly from that of non-stored ones (5%). 6. The extreme lower and upper limits of infection rate estimated for artificially incubated Greater Rhea eggs were 4% and 40%, respectively, being higher than in poultry species. 7. It is concluded that collecting eggs soon after laying will reduce the risk of microbial contamination.