Acute unilateral monosymptomatic optic neuritis (ON) is a common first manifestation of MS if associated with multiple MS-like lesions on brain MRI and oligoclonal IgG bands (OB) in the CSF, whereas ON patients lacking these laboratory abnormalities are considered to have a good prognosis regarding future MS development. Several cytokines involved in immune regulation are upregulated in blood and even more noticeable in CSF in MS. To study a possible relation between cytokine profiles and presence versus absence of MS-like brain MRI lesions and CSF OB, we used in situ hybridization to examine mRNA expression of the proinflammatory interleukin-12 (IL-12), interferon-gamma, and tumor necrosis factor-alpha and the immune response downregulating IL-10, transforming growth factor-beta, and IL-4 in blood and CSF mononuclear cells (MNC) from 59 patients with untreated ON. There were no differences in numbers of MNC in blood or CSF expressing any of the cytokines under study, upon subgrouping the ON patients regarding presence (n = 31) versus absence (n = 28) of MRI lesions, presence (n = 45) versus absence (n = 14) of OB, or duration after onset of ON (<1 month, n = 30, versus >1 month, n = 29). Similarly, no differences were observed for numbers of myelin basic protein-reactive blood MNC expressing any of these cytokines after subgrouping according to these variables. Our findings suggest that the cytokine profile, as examined in this study, is less useful to determine the risk of future development of clinically definite MS in ON patients or as indicator for therapeutic interventions in ON. An upregulation of both pro- and anti-inflammatory cytokines in ON patients seems to be more related to the CNS disease per se, whether limited to the optic nerve or not, than to the inflammatory process characteristic for MS.