The "NYU Simon Task" dataset comprises data collected from 21 healthy adults (age and sex included in AGE_SEX.txt) while they performed a rapid event-related Simon task. **Please note that all data have been uploaded regardless of quality- it is up to the user to check for data quality (movement etc). On each trial (inter-trial interval (ITI) was 2.5 seconds, with null events for jitter), a red or green box appeared on the right or left side of the screen. Participants used their left index finger to respond to the presentation of a green box, and their right index finger to respond to the presentation of a red box.In congruent trials the green box appeared on the left or the red box on the right, while in more demanding incongruent trials the green box appeared on the right and the red on the left. Subjects performed two blocks, each containing 48 congruent and 48 incongruent trials, presented in a pre-determined order (as per OptSeq), interspersed with 24 null trials (fixation only). Behavioral data is organized in 4 conditions, in subXXX/behav/taskXXX_runXXX/: # added by LNK on Apr 2010: cond001 - congruent_correct cond002 - congruent_incorrect cond003 - incongruent_correct cond004 - incongruent_incorrect Functional imaging data were acquired using a research dedicated Siemens Allegra 3.0 T scanner, with a standard Siemens head coil, located at the NYU Center for Brain Imaging. We obtained 151 contiguous echo planar imaging (EPI) whole-brain functional volumes (TR=2000 ms; TE=30 ms; flip angle=80, 40 slices, matrix=64x64; FOV=192 mm; acquisition voxel size=3x3x4mm) during each of the two simon task blocks. A high-resolution T1-weighted anatomical image was also acquired using a magnetization prepared gradient echo sequence (MPRAGE, TR=2500 ms; TE= 3.93 ms; TI=900 ms; flip angle=8; 176 slices, FOV=256 mm). These data have not been published previously.