Aim To explore the time course of expression of ICAM-1 gene and protein in macrophages foamy process induced by ox-LDL. Methods Cell cycle of Human myeloid leukemia U937 cells was arrested in G1 by preincubated with thymidine (2.0 mmol/L) for 24 h, then cells released at the same time. U937 cells were incubated with ox-LDL (80 mg/L) for time course(12 h, 24 h, 48 h or 72 h) treatment. Results Flow cytometric analysis results revealed that ICAM-1 protein expression increased from 12 h to 24 h and was highest at 24 h, but ICAM-1 decreased at 48 h. RT-PCR results showed that ICAM-1 mRNA level increased consistently with protein expression. Conclusions These results proved that ox-LDL could increase ICAM-1 gene and protein expression on U937 cells. Accumulation of cholesteryl esters in U937 cells has no negative feedback control on ICAM-1 gene and protein expression.