A series of 14 infants and small children ranging from 7 months to 7 years in age (mean, 2.5 years) underwent implantation of transvenous pacemaker systems. Three factors are of utmost importance in children: small subclavian vein size, thin subcutaneous layer in the chest, and growth. A five-point protocol is followed strictly: (1) duplex assessment of upper veins, (2) use of active fixation leads, (3) use of short (36 to 45 cm) leads, (4) anchoring of pulse generator with nonabsorbable material to prevent migration, and (5) routine use of the "lateral approach" in children more than 2 years old when the pulse generator is implanted in the chest. Because lead diameters measure 2 to 2.3 mm, a one-lead system needs a vein diameter of 5 mm (cross-sectional area of 19 mm2). A two-lead system needs a vein at least 7 mm in diameter and a cross-sectional area of 38 mm2 to prevent vein occlusion. Therefore all children less than 3 years of age had the leads implanted via the internal jugular vein. In 50% of children between 4 and 7 years of age, the internal jugular system also was used. Children more than 7 years old have leads implanted via the subclavian veins. Duplex ultrasound assessment of the upper veins is important to decide route of implantation. Use of short leads is recommended to reduce bulk at the pulse generator site. The "lateral approach" prevents problems at the generator implantation site.