Many organisms have been shown to have periodic behaviours. In fungi, sporulation and transport of cytoplasmic contents have been shown to have periodic behaviour that is genetically determined. We examined growth of the fungus Mucor mucedo as part of a project comparing the response of the fungus to differing ratios of carbon to nitrogen. We expected a smooth exponential initial growth phase which would plateau as nutrients were depleted. The data better fitted an exponential curve with a sinusoidal overlay of 28 hours duration. The possibility that growth and other physiological processes were out of phase, or offset, thus preserving a linear energy outlay was next tested. The formation of melanin by a different isolate of Mucor was in phase with the growth of the organism: both followed the same sinusoidal pattern overlying an exponential curve. This pattern has been noted in the growth of single members of the Ascomycontina and Basidiomycotina, and may be a generalised phenomenon.