A cytogenetic investigation was carried out on 39 Argentinean Creole cattle (8 bulls and 31 cows) from the Experimental Station in Chamical (La Rioja, Argentine). Heparinised blood sam- ples were cultured using a method of Moorhead et al. with some modifications. Karyotypes were es- tablished using a chromosomal digital analyser. A presumptive 1/29 Robertsonian translocation was found in one bull which had 2n = 59 chromosomes. The remaining animals appeared chromosomally normal. The 1/29 translocation has been diagnosed in other Creole breeds in America but never in Ar- gentine. The Y chromosome of the sampled bulls had the typical sub-metacentric structure normally occurring in Bos taurus. It is suggested that programmes for genetic and reproductive improvement incorporate chromosomal analysis of bulls and cows with a high genetic value for natural and artifi- cial breeding. Individuals with chromosomal abnormalities could then be eliminated, helping to as- sure the high fertility rates of this breed.