Currently, there is a surge of interest on the possible relationship between cancer and acid phosphatase locus 1 (ACP(1)), an enzyme involved in the modulation of growth factors and cellular metabolism. As far as the authors know, the possible relationship between ACP(1) genetic variability and cancer grading has not yet been considered. In this article, the authors have studied the relationship between ACP(1) genotype and grade in colon and endometrium cancers.Seventy-one patients with colon cancer and 71 patients with endometrium cancer were studied. ACP(1) genotype was determined by DNA analysis. Three-way contingency table analysis was carried out according to Sokal and Rohlf. Other statistical analyses were performed using SPSS programs.There is a significant association between ACP(1) and cancer grade mainly due to ACP(1) genotypes carrying the *C allele that are much less represented in patients with low grade when compared with those with high grade. In both cancers, the concentration of S isoform is significantly lower in low grade than in high grade. The relationship between ACP(1) and grade is the same in the 2 cancers.Assuming the presence of diverse classes of cancer, the role of ACP(1) in the modulation of growth factors and cellular metabolism could have significant effects in less aggressive forms but not in more aggressive ones.