BACKGROUND AND AIM: Although phthalates are still widely used, phthalate alternatives are replacing their use in food packaging, toys, and personal care products. However, data on sociodemographic and dietary predictors of concentrations of phthalate alternatives in children are limited. METHODS: We studied 830 children ages 6-10 years from 2007-2010 in Project Viva, a Boston-area cohort. We measured urinary phthalate metabolites and summed metabolites to calculate concentrations of ten parent phthalate diesters and alternatives. We determined average daily intake of 12 food groups over the prior month via a PrimeScreen questionnaire. We used linear regression to examine mutually adjusted associations of sociodemographics and diet with individual phthalates and alternatives, accounting for specific gravity. We used logistic regression to examine predictors of 1,2-cyclohexane dicarboxylic acid, diisononyl ester (DINCH) detectability. RESULTS:Participants were mean (SD) 7.8 (0.8) years; 67% had college-educated mothers. We detected at least one DINCH metabolite in 35% of samples and at least one metabolite of all other phthalates in ≥ 94% of samples. Sociodemographics and diet explained 25% (for di-isodecyl phthalate) to 48% (for di-n-butyl phthalate) of phthalate variability. The phthalate alternative di-2-ethylhexyl terephthalate was higher in girls (18.7% [95% CI: 0.7, 39.9]), children who consumed more meat and dairy (e.g. 36.9% higher [95% CI: 3.8, 80.6] for ≥ daily vs daily meat consumption), and samples from later years (e.g., 373.4% higher [95% CI: 220.9, 598.4] for 2010 vs. 2007). DINCH was more likely to be detectable in girls (odds ratio [OR] 2.1 [95% CI: 1.5, 3.0]) and samples from later years (e.g., OR 8.5 [95% CI: 3.6, 21.2] for 2010 vs. 2007). CONCLUSIONS:Sociodemographics and diet explained moderate variability of phthalate and alternative concentrations in children. We found higher concentrations of phthalate alternatives in girls and in samples from later years. Future studies should continue to investigate health effects of phthalate alternatives. KEYWORDS: Phthalates, Children's environmental health, Endocrine disrupting chemicals