Statement of problem: Studies determining the main predictors of masticatory performance by using mixing ability tests are sparse. Purpose: The purpose of this clinical study was to identify potential determinants of masticatory performance assessed by analyzing a patient's masticatory ability using bicolored chewing gum and visual, quantitative, and interactive methods. Material and methods: Nondental participants attending healthcare centers were consecutively recruited in Granada, Spain. The inclusion criteria were older than18 years and resident in the coverage area of the reference healthcare centers for at least the previous 6 months. The participants were excluded if they had received dental treatment in the previous 6 months or they were unable to communicate. The masticatory performance was determined by using 2-colored chewing gum (Kiss 3 white and blue; Smint) that was masticated for a total of 20 strokes. The masticated gum was crushed between 2 transparent glass slides, creating a 1-mm-thick specimen that was subsequently scanned. The mixed-color area was calculated as a percentage by using Photoshop as described by Schimmel et al and designated as the gold standard method. In addition, all images made were analyzed by using the Web application the Chewing Performance Calculator. In addition, the masticated bolus was inspected visually, and mastication performance was classified as being poor, moderate, or good. Sociodemographic data, as well as data on behaviors, medical and nutritional status, health-related quality of life, saliva, and general oral health, were collected for all participants to identify the main determinants of masticatory performance. Results: One hundred thirty-seven participants were enrolled. The masticatory performance values obtained using both methods (gold standard method and Chewing Performance Calculator) were significantly greater for well masticated gum (P<.001), which had been visually classified as being poorly masticated (69.1% for gold standard method and 43.5% for Chewing Performance Calculator), moderately masticated (89.7% for gold standard method and 67.3% for Chewing Performance Calculator), and well masticated (97.3% for gold standard method and 80.3% for Chewing Performance Calculator). The bivariate analyses revealed that masticatory performance was significantly higher in younger people (<65 years) (P=.008), who also had a higher basal salivary flow rate (P<.001), were nondenture users (P=.002), and had more standing teeth and occlusal units (P<.001). However, the multiple regression analyses showed that the number of occlusal units was the only significant predictor of masticatory performance. In addition, the mean masticatory performance (95% confidence interval: 47.7% to 56.8%) was found to be greatly improved (by 1.2% to 2.2%), with each occlusal unit, in accordance with the Chewing Performance Calculator and between 0.8% and 1.8% according to the gold standard method; the basal masticatory performance was calculated as 72.1% to 81.2% (95% confidence interval). Conclusions: The number of occlusal units is one of the main predictors of masticatory performance when a 2-color bolus is used to test mixing ability.