Posterior permanent teeth with carious lesions radiographically extending no further than halfway into dentin (N = 565) were restored by 38 dentists in a practice-based research network, using a resin-based composite. Preoperative and 1-, 4-, and 13-week posttreatment hypersensitivity was recorded with an 11-point visual analog scale that was completed anonymously by participants. The analyses determined whether any correlation or association existed among several variables, including degree of carious activity; cavity extent; application of antimicrobial or desensitizing agents; application of liner, dentin-bonding agent and resin-based composite employed; and composite placement method. Three results were fairly unexpected: Only 36% of lesions were ranked as caries-active, 31% of teeth had appreciable preoperative hypersensitivity, and 16% of teeth with no preoperative hypersensitivity had appreciable hypersensitivity at 1 week posttreatment. Preoperative hypersensitivity was correlated with lesion visibility on radiographs but not with dentin caries activity (ranked on opening enamel), preparation depth, or preparation volume. Accrual to the study continues, and conclusions regarding other relationships await 13-week results.