A prospective, controlled study was performed to compare side effect incidences after lumbar iohexol myelography (n = 97) and diagnostic lumbar puncture (n = 85). No significant side effect incidence differences (iohexol vs. controls) were found regarding number of patients with any side effect (63 vs. 73%), headache (44 vs. 54%), nausea, dizziness, visual, auditory, or psychic symptoms. Early-onset headache occurred significantly more often in the iohexol group (17 vs 5%), while postural headache occurred most frequently after lumbar puncture (25 vs. 41%). These results suggest that apart from the slight early-onset headache, most side effects after lumbar iohexol myelography are related to the puncture per se, not to the contrast agent.