Thirty-gauge needles are generally not recommended by dental schools, yet many dentists use them. Thin needles (30 gauge) can aspirate blood, have similar deflection to thick needles (25 gauge), and resist breakage. Measurable clinical differences between inferior dental block injections using 25-gauge or 30-gauge short needles for children is addressed in this research paper. Random allocation assigned 76 cases to 30-gauge and 62 cases to 25-gauge tribeveled. Twenty-seven-gauge short needles are in routine use for inferior dental nerve block injections in our clinics. After informed written consent was obtained, inferior dental block injections were carefully administered to children (62 males and 76 females, mean age 10 years ± 3 [SD], range 4-18 years) by faculty and students in pediatric dentistry and observed by one of two trained observers. After aspiration in two planes (180°), 0.5 mL of 2% lidocaine with 1:100,000 epinephrine was deposited in the lingual block area then 1.0 mL in the inferior dental area after touching bone. Any aspirate was recorded and subjective pain scores were taken immediately using a visual analogue scale. Five minutes after the commencement of the injection, the efficacy was tested objectively by two light needle pricks of the mucosa adjacent to the cuspid. The comparability of groups as regards age and sex was verified. Half of the injections were effective at five minutes in each group. There were no significant differences in efficacy, or pain scores. Both 25- and 30-gauge groups had nine instances of slight aspiration and two instances of more marked aspirations. The overall aspiration rate was 16%. It is concluded that 25- and 30-gauge needles do not differ significantly with respect to efficacy, pain, or aspiration. Children do not think that inferior dental nerve block injections hurt very much, and there is no evidence to support a change from 25- to 30-gauge needles.