Objective:To investigate the alteration of cell proliferation and tazarotene-induced gene 3(TIG3) mRNA level in cultured normal human keratinocytes after tazarotene and narrow-band UVB(NB-UVB) combined treatment or alone. Methods:Normal human keratinocytes were exposed to NB-UVB(50-100 mJ/cm2) and/or followed incubation with tazarotene(0.1-1 μmol/L) for 24 hours,then the proliferation potency of the cells was detected by methyl thiazoleterazolium colorimetric assay and the level of TIG3 mRNA was examined by real-time quantitative reverse transcription polymerase chain reaction(RT-PCR). Results:Cultured keratinocytes proliferation was inhibited and TIG3 mRNA level was enhanced by both two doses of tazarotene single treatment but not by NB-UVB irradiation alone. Further,the higher dose of tazarotene showed more effects on inhibiting keratinocyte proliferation and elevating TIG3 mRNA level. Tazarotene-NB-UVB combination showed great effects on inhibiting keratinocyte proliferation and increasing TIG3 mRNA level,which were stronger than those induced separately. Conclusion:Tazarotene incubation single can inhibit keratinocyte proliferation and enhance TIG3 mRNA level,but NB-UVB irradiation alone can’t. Tazarotene-NB-UVB combination showed synergistic effects on inhibiting keratinocyte proliferation and increasing TIG3 mRNA level.