Recent progress of our µSR measurements on high-TC and related systems is presented. Static magnetic order has been found and studied in La2CuO4, (La2-xSrx)CuO4, YBa2Cu3Ox, YBa2 (Cu3-xCox) O7, as well as in Bi2Sr2YCu2O8. No magnetic order was found in the 3-dimensional systems BaBiO3, Ba(Pb0.1Bi0.9) O3, and (BaK) BiO3 above T = 10 K. The anisotropy of the magnetic field penetration depth λ has been observed by using a c-axis alligned sintered pellet specimen of YBa2Cu3O7. The temperature dependence of λ|| (for c || Hext) indicates isotropic superconducting energy gap without any anomalies. Based on the muon spin relaxation rate σ observed in (random) pellet specimens of various high-TC superconductors, we found a linear relation between TC and σ α 1/λ2 α ns/m*, which suggests a high energy scale of superconducting coupling. Deviations from this linear relation are seen for samples with large carrier concentrations ns