The purpose of this study was to determine dietary diversity and its relation to dietary adequacy in 10-18 year-old adolescents of district 13 of Tehran during the period 1999-2001. After excluding for over and under reporters, dietary intake assessment was conducted on 304, 10-18 year old individuals, participants of Tehran Lipid and Glucose Study. A dietary diversity score was calculated as part of the pyramid serving database that is categorized into 23 broad food groups. Each of the 5 broad food categories received a maximum diversity score of 2 of the 10 possible score points. To be counted as a "consumer " for any of the food groups categories, a respondent needed to consume one-half serving, as defined by Food Guide Pyramid quantity criteria, at any time during a 2-day survey period. The nutrient adequacy ratio for a given nutrient is the ratio of a subject's intake to the current recommended allowance for the subject's sex and age category. Weight and height were measured and BMI was calculated. Student's t-test was used to compare the means. Those variables which had normal distribution were tested by Pearson correlation coefficient and the others were tested by the Spearman correlation coefficient. Mean +/-SD of dietary diversity score (DDS) was 6.25 +/- 1.08 (range 0-10). The maximum and minimum scores of dietary diversity were related to the fruit (1.46+/-0.61) and bread-grain (0.95+/-0.27) groups, respectively. Significant positive correlation was observed between DDS and the mean adequacy ratio (MAR) (r =0.42, P <0.001). Fifty percent of people had DDS >or = 6. In people with a DDS of six or over, BMI was higher (19.81 +/- 4.08vs18.95+/- 3.30 Kg/m(2), P<0.01) than others. There was a significant and positive correlation between DDS and most of the nutrient adequacy ratios (NARs). It is concluded that DDS is an appropriate method to evaluate nutrient intake adequacy in this group of adolescents.