Entamoeba histolytica (HK-9: IMSS) trophozoites were separated from the culture medium and washed and submitted to the effects of ultrasound during 10 minutes. After 10,000 rpm x 30 centrifugation, the supernatant fluid was separated in four fractions by Sephadex G-200 gel chromatography. These fractions were lyophilized, redisolved in a lesser volume and dyalized against isotonic saline solution. Antigen-antibody precipitant reactions between each of them and two rabbit antiserums were demonstrated: anti amoeba and anti fraction A. It was verified that the antisera reacted also with the culture medium, the human seric albumin and the sera from health people and patients with invasive amebiasis. The higher antigenicity, quantitatively and qualitatively, was obtained with the fraction B; the less antigenic fraction was the fraction D. In fraction A three antigens were identified. When those proteins were filtered by a Bio Gel P4 column, two fractions were eluted: A1 and A2 which were lyophilized, redisolved and dyalized in isotonic saline solution. After this treatment, fraction A1 was capable to maintain its antigenicity against the rabbit antisera and the sera from patients with invasive amebiasis, fact by which it was considered a protein from amebal origin and not as a protenic contaminant from the culture medium.