Marijuana use has become more widely accepted in the United States and has been legalized in many areas. Although it is biologically plausible that marijuana could affect kidney function, epidemiologic data are lacking. We conducted a cohort study among young adults with preserved eGFR (i.e., eGFR≥60 ml/min per 1.73 m2) using data from the Coronary Artery Risk Development in Young Adults (CARDIA) study. At scheduled examinations occurring every 5 years and starting at study year 10 (calendar years, 1995-1996), cystatin C was collected over a 10-year period, and urine albumin-to-creatinine ratio was collected over a 15-year period. We investigated the cross-sectional association between current and cumulative marijuana use (in marijuana-years; one marijuana-year equals 365 days of marijuana use) and eGFR by cystatin C (eGFRcys) at year 10. In longitudinal analyses, we investigated the association between cumulative marijuana use and eGFRcys change and rapid (≥3%/year) eGFRcys decline over two 5-year intervals and prevalent albuminuria (urine albumin-to-creatinine ratio ≥30 mg/g) over a 15-year period. Past or current marijuana use was reported by 83% (3131 of 3765) of the cohort, and the mean eGFRcys was 111 ml/min per 1.73 m2 at year 10. Over the following 10 years, 504 had rapid eGFRcys decline, and over the following 15 years, 426 had prevalent albuminuria. Compared with no use, daily current use and ≥5 marijuana-years of cumulative use were associated with lower eGFRcys at year 10: -4.5% (95% confidence interval, -8.1 to -0.7%; P=0.02) and -3.0% (95% confidence interval, -5.6 to -0.4%; P=0.03), respectively. Marijuana use was not significantly associated with eGFRcys change, rapid eGFRcys decline, or prevalent albuminuria. Although we identified a modest cross-sectional association between higher marijuana exposure and lower eGFRcys among young adults with preserved eGFR, our findings were largely null and did not demonstrate a longitudinal association between marijuana use and eGFRcys change, rapid eGFRcys decline, or prevalent albuminuria. This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2017_08_24_CJASNPodcast_17_10.mp3.