Changes in liver cytosol cAMP-dependent kinase and cAMP-independent growth-related quercetin-inhibited casein kinase activities during chick embryo development were studied. 2. Both kinase activities were found to increase continuously during the experimental period. 3. Upon treatment of embryos with triiodothyronine, an activation of cAMP-dependent kinase A and cAMP-independent casein kinase was observed which was most pronounced on days 12 and 14.