Recent work on circadian clocks in
Neurospora
has primarily focused on the
frequency
(
frq
) and
white–collar
(
wc
) loci. However, a number of other genes are known that affect either the period or temperature compensation of the rhythm. These include the
period
(no relationship to the
period
gene of
Drosophila
) genes and a number of genes that affect cellular metabolism. How these other loci fit into the circadian system is not known, and metabolic effects on the clock are typically not considered in single–oscillator models. Recent evidence has pointed to multiple oscillators in
Neurospora
, at least one of which is predicted to incorporate metabolic processes. Here, the
Neurospora
clock–affecting mutations will be reviewed and their genetic interactions discussed in the context of a more complex clock model involving two coupled oscillators: a FRQ/WC–based oscillator and a ‘
frq
–less’ oscillator that may involve metabolic components.