We present a novel system for detecting electroencephalographic transient events in neonates and older children. The detection system consists of three major elements: (i) a preprocessing stage for filtering EEG and detecting artifacts, (ii) a hierarchical course-to-fine temporal event detection stage and (iii) a hierarchical course-to-fine spatial event selection stage to incorporate spatial contextual information for rejection of spurious events. The output consists of homogeneous EEG events and their corresponding dipole clusters. The system was evaluated on EEG signals recorded in four neonates and six older children. There was a high degree of correlation between system-detected and expert-marked events for all patients. Mean sensitivities of 84.9% and 91.9% and mean selectivities of 86.3% and 90.6% were obtained for the neonates and the older children, respectively. This tool is appropriate for the detection and selection of homogeneous EEG events prior to source localization. Quantitative spatial analysis of dipoles may facilitate the physician's assessment of patients' brain dysfunction.