We applied antisense RNA technology for reducing the level of human IFN-gamma (HuIFN-gamma) expression. An antisense RNA vector containing the full-length HuIFN-gamma cDNA in the opposite orientation was electroporated into cells constitutively producing very high levels of the cytokine. Approximately 53% of the resulting clones exhibited a specific HuIFN-gamma inhibition of an average of 95.5%. The results of reverse transcription-polymerase chain reaction and Northern blot analyses revealed that the antisense effect originated from a specific reduction of the targeted mRNA caused by antisense RNA expression. This very effective antisense RNA strategy can have possible therapeutic applications in treating diseases where HuIFN-gamma is known to play a negative role, such as in certain autoimmune diseases.