The precursor-mRNA transcribed from the chicken apo very low density lipoprotein II gene was identified. This gene which is under full estrogen control and only expressed in the liver, possesses three introns. Splicing intermediates were characterized by hybridization with intron-specific probes, and by electron microscopy of R-loops. The introns appear to be excised in a non-obligatory order, but at different rates. APO-VLDL ZZRNA splicing Estrogen Yolk protein gene