The purpose of this study was to evaluate the shear bond strength of glass ionomer cement(Ketacfil, ESPE, Co.) against dentin surface which had been treated with surface conditioning agents(distilled water, 5% sodium hypochlorite solution, Ketac - conditioner, 40% polyacrylic acid). In this study, 60 human molars with sound and healthy crown portion which were previously extracted for orthodontic or periodontal problem. The dentin surfaces of these teeth were exposed with wet trimmer and polished with 150 - grit and 600 - grit silicon carbide paper and the teeth were divided into four groups(15 teeth per group) according to the following surface conditioning methods. Group I : Surface treatment with distilled water as control group. Group II : Surface conditioning with 5% sodium hypochlorite solution. Group III : Surface conditioning with Ketac conditioner. Group IV : Surface conditioning with 40% polyacrylic acid. The shear bond strengths were measured by Autograph(Shimatzu Co. Japan). The result of the evaluations were then subjected to statistical analysis using one - way analysis of variance and Duncan test and the results were as follows : 1. The shear bond strength accrding to the dentin surface conditioning conditions was highest in Ketac conditioner group, with measurements of $44.44{pm}0.74(kg/cm^2)$ and lowest in the distilled water group, with measurements of $28.84{pm}0.88(kg/cm^2)$. 2. Statistically significant differences were found between surface conditioning with 5% sodium hypochlorite solution group or Ketac conditioner group and distilled water group(P<0.01). 3. Also, statistically significant difference was found between surface conditioning with distilled water group and 40% polyacrylic acid group(P<0.05). 4. Overall difference in statistical significance between the groups was not found (P<0.05). 5. Fractured dentin surface treated with conditioning solutions showed cohesive fracture. 6. Distilled water group and 5% sodium hypochlorite solution group removed the smear layer less effectively. 7. Conditioning dentin with Ketac conditioner and 40% polyacrylic acid resulted in the removal of a significant amount of the smear layer without removing the tubular plugs and dissolving the peritubular dentin.