The aim of this study was to evaluate the effect of formalin cresol on bonding of two compomers (Prime & Bond and Dyract, Futurabond and Glasiosite to primary dentine. Eighteen non-carious primary mandibular molar teeth were used. The two materials were placed onto the tooth surfaces before being sheared with a knife-edged blade with a crosshead speed of 1 mm min(-1). Two randomly selected teeth from each group were evaluated by scanning electron microscopy (SEM). The statistical analysis (paired t-test and Student's t-test) revealed that shear bond strength was significantly higher in the formocresol-applied group than in the group that was not applied formocresol (P < 0.05), but there was no significant difference between the restorative materials. SEM analyses also supported the results obtained. In conclusion, if compomers are used after endodontic processes which require the application of formocresol in primary teeth, dentinal bonding would not be decreased, but on the contrary, increase.