A two-dimensional high angular resolution study of Omicron Ceti (Mira), carried out at four epochs from November 1983 to November 1988 using speckle interferometry techniques, detected asymmetries in the extended atmosphere of this pulsating star. The reconstructed speckle images show that the strength and the shape of this asymmetry changes as a function of wavelength and time. The position angles of the major axes of the asymmetries at different epochs are determined and the axes were measured accurately as a function of wavelength. The origin of the observed asymmetries has not yet been identified. Plausible causes include instabilities in the pulsating atmosphere, nonspherical pulsation, or the interaction with the nearby companion.