Determining the viability of an egg by: (a) causing electromagnetic radiation, having one or more wavelengths in the infra-red part of the spectrum, to impinge upon the egg; (b) receiving at least a part of the infra-red radiation that has passed through the egg and generating an output signal representative of the received infra-red radiation; and (c) processing said output signal to determine whether there is a cyclical variation in the intensity of the infra-red radiation leaving the egg corresponding to action of a heart, the existence of said cyclical variation indicating that the egg is viable; wherein step (a) is performed by directing infra-red radiation so that it passes through the shell for reflection from an outer surface of a vascular structure adjacent an inner surface of said shell, and step (b) is performed by receiving any infra-red radiation so reflected.