General concepts / Amita Sehgal -- Genetic and molecular approaches / Amita Sehgal and Jeffrey L. Price -- Drosophila melanogaster / Jeffrey L. Price -- Circadian clocks in non-mammalian vertebrates / Julie A. Williams -- Genetic basis for circadian rhythms in mammals / John D. Alvarez -- Circadian rhythms in cyanobacteria / Nirnjini Naidoo -- Molecular analysis of circadian rhythms in neurospora / Amita Sehgal -- Physiological and molecular characteristics of plant circadian clocks / Jose A. Jarillo, Juan Capel, and Anthony R. Cashmore -- Multiple oscillators / Jadwiga M. Giebultowicz -- Hormonal rhythms / Peter McNamara -- Human circadian rhythms / Hans P.A. van Dongen, Gerard A. Kerkhof, David F. Dinges.