The present invention relates to compositions and methods for delivery of antisense oligonucleotides or other nucleic acid sequences. The present invention comprises a delivery composition comprising an administerable admixture of an effective amount of a nucleic acid sequence and an effective amount of a surface active nonionic block copolymer having the following general formula: HO(C.sub.2H.sub.4O).sub.b(C.sub.3H.sub.6O).sub.a(C.sub.2H.sub.4O).sub.bH wherein a is an integer such that the hydrophobe represented by (C.sub.3H.sub.6O) has a molecular weight between approximately 750 and approximately 15,000, preferably between approximately 2250 and approximately 15,000, more preferably between approximately 3250 and approximately 15,000, and b is an integer such that the hydrophile portion represented by (C2H4O) constitutes approximately 1% to approximately 50% by weight of the compound, preferably approximately 5% to approximately 25%.