Long noncoding RNAs (IncRNAs) play a broad range of biological roles, including regulation of expression of genes and chromosomes. Here, we present evidence that IncRNAs are involved in vertebrate circadian biology. Differential night/day expression of 112 IncRNAs (0.3 to >50 kb) occurs in the rat pineal gland, which is the source of melatonin, the hormone of the night. Approximately one-half of these changes reflect nocturnal increases. Studies of eight IncRNAs with 2-to > 100-fold daily rhythms indicate that, in most cases, the change results from neural stimulation from the central circadian oscillator in the suprachiasmatic nucleus (doubling time = 0.5-1.3 h). Light exposure at night rapidly reverses (halving time = 9-32 min) levels df some of these IncRNAs. Organ culture studies indicate that expression of these IncRNAs is regulated by norepinephrine acting through cAMP. These findings point to a dynamic role of IncRNAs in the circadian system.