A period-timeless (per-tim) based feedback loop is considered to be essential in generating circadian rhythms in Drosophila melanogaster. In addition to transcriptional regulation, the post-transcriptional modification is essential to the circadian oscillation of core clock proteins in the circadian system. Here we present expression profiles of the catalytic subunit of casein kinase 2alpha (ck2alpha) and casein kinase 2beta (ck2beta) in Bombyx mori. Southern blot analyses showed that ck2alpha and ck2beta of B. mori were single copy genes. Northern blot analyses demonstrated that both subunits were expressed in eggs, larval heads, adult heads, testes and ovaries. In situ hybridization analyses indicated that subunits were expressed in brain neurons expressing PER-like protein. Surprisingly, antisense RNAs of ck2alpha and ck2beta were also detected in the putative clock neurons. Temporal expressions of ck2alpha and ck2beta mRNAs were constant in adult heads under LD12:12. The core clock genes per and tim showed daily fluctuations of mRNA abundance in the embryonic stage that is photoperiod sensitive period to determine egg diapause in the next generation whereas the expression of ck2alpha and ck2beta was constant. No evidence supports that ck2alpha and ck2beta of B. mori were transcriptionally regulated by circadian oscillation, but histological data show a close association of ck2alpha and ck2beta with circadian system in B. mori.