The start of the 2nd year is a period of transition and substantial variability among toddlers in play and attention abilities. This longitudinal study examined the antecedents of variation among 13-month-old toddlers in these exploratory competencies in the infants' own information-processing abilities at 5 months (indexed by visual fixation in the laboratory], the infants' vocal and exploratory activities at 5 months (measured during naturalistic observation in the home), mothers' stimulation of infants at 5 months, and mothers' IQ. Infant visual fixation and maternal IQ predicted toddler symbolic play; furthermore, infant visual fixation, infant activity, and maternal IQ predicted toddler attention span. In contrast, mothers' early stimulation did not predict play or attention in toddlers. Structural equation modeling was used to assess prediction of the three significant antecedents (infant visual fixation, infant activity, and maternal IQ) to toddlers' exploratory competence, a latent variable representing the shared variance between play and attention. Together, the three predictors accounted for 50% of the variance in toddler exploratory competence. These data broaden the scope of infant and mother prediction beyond toddler verbal-representational abilities to encompass domains of toddler exploration.