neurons in the supplementary eye field of rhesus monkeys code visual targets and saccadic eye movements in an oculocentric coordinate system 1 we investigated whether neurons in the supplementary eye field sef of macaque monkeys code saccadic eye movements in oculocentric coordinates relative to the current direction of fixation or in craniocentric coordinates relative to the head craniocentric coding in sef had been previously suggested by the convergent appearance of electrically elicited saccades originating at different orbital positions 2 we primarily studied sef neurons that started responding before the beginning of saccades because such presaccadic activity is likely related to saccade generation and metrics using a memorysaccade task we classified the presaccadic activity of each neuron as either purely visual related purely movement related or both visual and movement related 3 we then mapped the response fields receptive fields and movement fields of sef neurons from different orbital positions when mapped relative to a central fixation point the strongest responses for a given sef neuron invariably occurred for a particular polar direction with fairly symmetrical declines for departures from that direction when tested using other fixation point locations their strongest responses almost always continued to occur for stimuli having the same polar direction relative to each fixation point tested and thus they appeared to code both stimulus direction and saccade direction in an oculocentric coordinate system 4 the effect of eye position on sef presaccadic activity was quantified in two ways by computing for each neuron 1 an intersection distance the eccentricity of the point where extensions of the neurons optimal polar directions measured at two eccentric orbital positions converged and 2 an orbital perturbation index such that an index of 0 corresponded to no change in the neurons optimal polar direction across different orbital positions ie perfectly oculocentric response fields and an index of 1 corresponded to optimal polar directions that converged to the same craniocentric goal regardless of initial eye position ie perfectly craniocentric response fields for neurons with both visual and movement responses these measures were calculated separately for each type of activity using tasks that temporally separated the visual cue presentation and the saccade to it 5 almost all of the intersection distances were well beyond the oculomotor range 50 degrees of the monkey 3839 for movement activity and 6266 for visual activity the median intersection distance for visual activity was very large 274 degrees and the median for movement activity was slightly divergent beyond infinity thus sef neurons rarely showed a conspicuous convergence of response field direction 6 likewise the mean orbital perturbation indexes were very small 004 021 mean sd for movement activity and 009 015 for visual activity also indicating that sef neurons code stimuli and saccades in an oculocentric manner 7 for neurons with both visual and movement activities the orbital perturbation indexes of the two activities were not significantly correlated r 016 even though their characteristic directions optimal polar direction estimated from the center of the