A diaphragm for a diaphragm pump, which diaphragm is asymmetrical about its longitudinal axis wherein the diaphragm has a central portion and a surrounding annular convolute portion. The convolute portion has a minimum depth and a maximum depth at diametrically opposed positions of the annular convolute. The convolute depth gradually increases from the minimum depth to the maximum depth between the diametrically opposed positions along each opposing half-section of the annular convolute. The invention also provides a diaphragm pump with the asymmetrical diaphragm.