The purpose of this study was to evaluate the sensitivity of 4 clinical techniques used in detecting early plaque during a period of dietary sucrose restriction and during a period of sucrose supplementation. The accumulation of plaque during experimental periods of 3 h, 6 h and 18 h was recorded in a group of 38 dental personnel for the 1st part of the study, and in a group of 32 for the 2nd part. Plaque levels were assessed using a caries probe, a plaque detection probe, erythrosin and a 2-tone disclosing agent. There was a progressive increase in plaque over the period of the study, with significant variation between the detection methods used and the sites being assessed. Plaque formed more rapidly interdentially and on the posterior teeth. 3 h after the teeth had been thoroughly cleaned, plaque was detectable on over 12% of sites for the sucrose-restricted diet and on up to 23% of sites for the sucrose-supplemented diet. After 18 h of plaque formation, the proportion of plaque-covered surfaces had increased to between 52% and 73%. For minimal amounts of plaque, the disclosing solutions were found to be the most sensitive assessment techniques. However, for moderate and abundant plaque deposits, the techniques using the probes resulted in a greater degree of differentiation in the proportional measurements of plaque. Overall, the plaque probe was found to be as sensitive or better than the other techniques under most conditions and was favoured on clinical grounds, as it aided access to the interdental areas and provided a contrasting colour at the tip to enable plaque to be detected with greater ease.(ABSTRACT TRUNCATED AT 250 WORDS)