Rhythmic activities in electroencephalography (EEG) have been extensively studied in adults and classic rhythms are found to correlate with specific human brain functions. However, less has been investigated in infant EEG, and EEG rhythms in infants at early ages have not been well characterized in terms of their frequency ranges. In the present pilot study, we investigated rhythmic activities in infant EEG recorded weekly from 4-8 months using high-density EEG sensor nets. The developmental changes of EEG rhythms in different frequency bands along maturation were evaluated through spectral analysis. Their longitudinal scalp maps were also studied to understand their plausible functional correlates. The present study aims to enrich the sparse knowledge about the developing patterns of EEG rhythms within the first year of life from EEG recordings of high temporal and spatial resolutions.