Using data from the 1979 National Longitudinal Survey of Youth (NLSY79), we investigate the college attendance, dropout, and graduate behavior of high school graduates. Bivariate duration models, which allow the unobserved determinants of spell durations to be correlated across spells, are developed and used to study the impact of the waiting time from high school graduation until college enrollment on college dropout and graduation rates. We find that delaying college entry after graduating high school significantly increases the chances of college dropout and reduces the probability of attaining a four-year degree. Among those who first enroll in four-year institutions, delaying college entry by one year after high school graduation reduces the probability of graduating with a four- year degree by up to 32 percent in models that account for the endogeneity of delaying enrollment. There is also empirical evidence that the negative impact of delayed enrollment on graduation probabilities varies by Armed Forces Qualifying Test (AFQT) score with the largest estimated impact of delaying occurring for those with low AFQT scores.