Ten and thirty cassava genotypes producing wildtype and amylose-free (waxy) respectively, were grown at low (LA) and intermediate (IA) altitudes (< 213 and < 900 meters above sea level-m.a.s.l., respectively). The functional properties of the starch from these materials were analyzed. The relative importance of environment, clones (within starch type) and genotype-by-environment interaction (GxE) was assessed through an analysis of variance. GxE effects were non-significant, whereas environment and clones (within starch type), were highly significant in most of the cases (particularly for waxy starches). Results confirm that waxy cassava starches consistently show higher peak viscosity (PV) compared with wildtypes. Peak viscosity was statistically higher in plants grown in IA compared with those from the same genotypes grown in LA, both for waxy and wildtype genotypes. In a second experiment, a single waxy genotype was grown in five locations ranging from 934 to 1485 m.a.s.l. PV was highest in the location with higher altitude. The second highest PV was measured in starches from the second highest location at 1071 m. Both experiments clearly indicate that PV is positively correlated with altitude above sea level where cassava was grown. Altitude above sea level influenced starch granule size: the higher the altitude the larger the average granule size. Waxy starch granules tended to be larger than those from wildtype genotypes.