Adolescent mothers of 8- to 14-month-old infants gave fewer correct responses on the Developmental Milestones Survey (DMS) and were less accurate in predicting whether or nor their infants would pass Bayley items than adult mothers of same-aged infants. Adolescent mothers were more likely to under estimate their infant's performance if the mothers received lower scores on the DMS, especially if they were likely to guess too young an age when they missed DMS items. Adult mothers, on the other hand, were more likely to underestimate their infant's performance if the mothers were likely to guess too old an age when they missed DMS items. Some adolescent mothers thus expect too little too late from their own infant and too much too soon from the average infant. These mothers may fail to encourage their infant's development and may perceive their infant as less competent than other infants because of these expectations.