The structural changes of crystalline atorvastatin upon high-energy ball milling at room temperature have been studied. The study investigates the effect of polyvinylpyrrolidone (PVP) and hydroxypropylmethyl cellulose (HPMC) polymeric matrix on stabilizing amorphous atorvastatin before and after storage under ambient and elevated humidity conditions. The materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), 19F MAS NMR spectroscopy, and dissolution testing. The results indicate that this drug has undergone a direct crystal-to-glass transformation upon milling. Stable amorphous form of atorvastatin calcium has been obtained with PVP and HPMC (in 1:1 ratios).