Recently there has been an increased interest in determining the circulating glucose concentration after the ingestion of various individual foods and mixed meals. The purpose of these determinations is to systematically rank foods with respect to their quantitative effect on postmeal glucose concentration. Potentially such data could be useful in designing a diet for individuals with diabetes. We believe this concept is good. However, several factors that may affect interpretation if the data used to develop this ranking need to be considered before the utility of this approach to dietary management can be assessed: 1) duration of time over which the data are collected and analyzed; 2) use of absolute versus incremental areas in the determinations; 3) inclusion or exclusion of negative areas if incremental areas are used; 4) differences in response to a given food in males compared with females; 5) severity of diabetes; 6) confounding effects of oral agents or insulin treatment; 7) reproducibility of data; 8) differences in collection of blood sample; 9) food composition, processing, and preparation; 10) the dose-response relationship to ingestion of a given carbohydrate; 11) the meal being studied, i.e., first, second, or third meal of the day; and 12) a possible effect of the composition of the previous meal, if the response is tested to any meal other than the first meal of the day.