Abstract: Ho0.1Ca0.9MnO3 is a canted antiferromagnet with the magnetic space group Pnma. The magnetic structure is a superposition CxFyAz of the three types of order allowed in Pnma. In the Ca-rich corner of the system Ho1-xCaxMnO3 the title compound has a strong magnetoelastic distortion , the highest metallic conductivity and a ferromagnetic component Fy close to the maximum in the series. Among the areas ab, bc, ca calculated from the lattice constants only ca shows a strong magnetoelastic effect below TN = 106 K. The x-, y-, z-spin components depend differently on the temperature. This gives rise to spin rotation which is particularly strong close to TN. MnO6 octahedra have short bond lengths with a temperature independent average . They are practically regular at room temperature and show a Jahn-Teller distortion of 3.5% in the magnetically ordered state. Above TN we find small polaron conductivity. The presence of the Jahn-Teller distortion due to the only small abundance (10%) of Mn3+ in the t2g3eg configuration is attributed to delocalised eg electrons. In the magnetically ordered state the averaged magnetic moment of Mn is reduced appreciably from the paramagnetic value due to spin disorder.