Oral clearance and acid production were observed in 30 volunteers following the ingestion of sharp cheddar cheese (CC) and in 9 volunteers following the ingestion of milk chocolate (MC) and low-fat yogurt, and then when MC was eaten immediately after CC (CC/MC) and when CC was eaten following MC (MC/CC). After each test food or food combination had been ingested the volunteers were monitored at five different tooth sites. At each site, using an absorbent paper point, 4 oral fluid samples were collected at 30 min intervals. The five paper points from each sampling occasion were pooled, extracted with 1 ml of water and analyzed qualitatively and quantitatively for both carbohydrates and organic acids using HPLC. Data obtained for each food was averaged and subjected to statistical evaluation. With the CC, glucose clearance was prolonged, due to intermediate lactose degradation into galactose and glucose. The quantity of lactic acid produced during the four intervals was monitored for each of the test foods and their combinations. Results: CC, MC, CC/MC, MC/CC 30 min after ingestion: 1.64, 3.47, 4.68, 2.97; after 60 min: 1.30, 1.24, 1.28, 1.43; after 90 min: 1.58, 1.02, 0.76, 0.43; after 120 min: 1.27, 0.90, 0.70, 0.42 mmol lactic acid/l oral fluid, respectively. The average total amount of lactic acid obtained during the two hour test period was (highest) CC/MC > MC > CC > MC/CC (lowest). The lowest amount of intra-oral lactic acid was observed (Student’s t test, p < 0.05) when cheddar cheese (CC) was eaten immediately after the milk chocolate (MC). Clinical Significance: Consumption of cheese (cheddar), immediately after a sweet meal, significantly reduces (approx. 30%) the amount of lactic acid produced in the oral cavity, when compared to the amount of acid obtained from the sweet food alone.