A cross-sectional study was conducted to determine the prevalence of Histoplasma farciminosum in 2,907 carthorses using clinical and microbiological examinations at three towns (Debre Zeit, Mojo and Nazareth), Central Ethiopia, between December 1999 and January 2001. An overall prevalence of 26.2% (762/2,907) was recorded; the highest prevalence (39.1%) being recorded at Mojo whereas the lowest (21.1%) was recorded at Nazareth. The difference in prevalence among the three towns was highly significant (chi(2) = 76.92, P<0.0001). Carthorses found at Mojo [OR =2.4, CI=(1.9-3.0), P<0.0001] and Debre Zeit [OR=1.9, CI=(1.5-2.3), P<0.0001] were at higher risk of infection than those found at Nazareth. The mycelial and yeast forms of the Histoplasma capsulatum variety farciminosum were isolated on the Sabouraud's dextrose agar. The results of the present study showed the rampant occurrence of histoplasmosis farciminosi at the three towns and indicates the need for further nationwide investigation into the disease to design sound control strategy.