OBJECTIVES:   The objective of this study was to determine the medication utilization rates of stimulant, antidepressant, and antipsychotic medications during the period 2002-2012 in Texas Medicaid children aged 0 to 3 years old. METHODS:   Texas Medicaid prescription claims data from 2002 to 2012 were analyzed for patients who were 3 years old or younger. Specifically, stimulant, antidepressant, and antipsychotic prescription claims were assessed to determine trends by age and gender. RESULTS: The number of Texas Medicaid patients 3 years old and younger ranged from about 830,000 in 2002 to 1.3 million in 2012.  From 2002 to 2012, the percent of children 3 years old and under prescribed stimulants increased from 0.10% to 0.11% (highest year 2011 at 0.14%).   For antidepressants, there was also an increase from 0.02% to 0.03% (highest year 2011 at 0.04%). In contrast, the percent of antipsychotic users decreased from 0.02% to less than 0.01% (highest year 2004 at 0.02%). On average, over the 10-year period, the majority of utilizers were male (73.6% stimulants, 69.4% antidepressants, and 74.6% antipsychotics), and percentages were similar from year to year. Three-year-olds represented the majority of medication users for each medication category, where they constituted more than 75.0% of all users, at any point from 2002 to 2012.  For patients 2 years old or younger, the stimulant utilization rate followed a generally steady decrease over the 10-year period, while the antipsychotic and antidepressant utilization rates increased from 2002, peaked (around 2006 and 2010, respectively), and then decreased thereafter. CONCLUSIONS: The use of stimulant and antidepressant medications in Texas Medicaid children three years old and younger increased from 2002 to 2011 but then decreased in 2012.  The use of antipsychotic medications in this age group peaked in 2004 and, overall, has been decreasing since then.