Background The combination of propofol and remifentanil may be particularly suitable for short-duration procedures such as lumbar puncture. The authors undertook a two-part study to evaluate coadministration of propofol and remifentanil as an anesthetic technique for lumbar puncture in children. Methods The first part was a sequential allocation dose-finding study to determine the minimum effective dose of remifentanil when coadministered with 2.0 or 4.0 mg/kg propofol. The second was a randomized double-blind study to compare the intraoperative and recovery characteristics of 2.0 or 4.0 mg/kg propofol coadministered with the corresponding effective dose of remifentanil. Results Effective doses of remifentanil in 98% of children were 1.50 +/- 1.00 and 0.52 +/- 1.06 microg/kg when coadministered with 2.0 and 4.0 mg/kg propofol, respectively. The duration of apnea was longer (median, 110 vs. 73 s; P < 0.05) and the time to awakening was shorter (median, 10 vs. 23 min; P < 0.05) after 2.0 mg/kg propofol plus 1.5 microg/kg remifentanil compared with 4.0 mg/kg propofol plus 0.5 microg/kg remifentanil. No child experienced hypotension or postprocedure nausea or vomiting after either dose combination. Conclusions Both dose combinations (2.0 mg/kg propofol plus 1.5 microg/kg remifentanil and 4.0 mg/kg propofol plus 0.5 microg/kg remifentanil) provide effective anesthesia for lumbar puncture in children. However, the intraoperative and recovery characteristics of the two dose combinations differ in that the duration of apnea increases whereas recovery time decreases as the dose of remifentanil is increased and that of propofol is decreased.