High-density single nucleotide polymorphism (SNP) array analysis revealed novel amplification at 1q21 in cell lines derived from hepatocellular carcinomas (HCCs). Fluorescence in situ hybridization and real-time quantitative polymerase chain reaction studies verified amplification at 1q21. An increase in copy number at the region was detected in 32 of the 36 primary HCC tumors (89%). To identify the targets for amplification, we examined 19 HCC cell lines for expression levels of all 26 genes located within the 700-kb amplified region. Five genes were overexpressed in cell lines with amplification at 1q21. Among these, CREB3L4 (cAMP responsive element binding protein 3-like 4), INTS3 (integrator complex subunit 3), and SNAPAP (SNAP-associated protein) were significantly overexpressed in tumors from 18 HCC patients, compared with counterpart nontumorous tissues. The findings suggest that CREB3L4, INTS3, and SNAPAP are probable targets for the amplification mechanism and may therefore be involved, together or separately, in the development or progression of HCCs.