We investigated TNF-alpha gene expression in HL-60 cells under the influence of 1,25(OH)2D3. Our results show that TNF-alpha gene expression is transcriptionally activated by 1,25(OH)2D3. Despite the increase of TNF-alpha mRNA, very little TNF protein is found in either supernatants or cell lysates of HL-60 cells cultured in the presence of the vitamin. Therefore 1,25(OH)2D3 is regulating the transcription of the TNF-alpha gene in HL-60 cells without affecting translation. Our data suggest that an additional signal is necessary under physiological conditions to control post-transcriptionally TNF-alpha protein synthesis and secretion.