A longitudinal study on primary tooth eruption was performed in 114 Spanish children in two Primary Care Centers over 3 yr. Data from periodic observations and data collected by previously instructed parents was studied. Ages of tooth eruption were calculated for both sexes. Comparison between the two sides of the jaws showed a nonsignificant tendency towards earlier left side eruption. Comparison between maxillary and mandibular showed a significant earlier mandibular eruption for central incisors and second molars and a significant earlier maxillary eruption for lateral incisors. Comparison between sexes showed a tendency towards earlier eruption in boys for all teeth, significant only for mandibular central incisors, maxillary and mandibular lateral incisors and mandibular canines. Order of tooth eruption and its most frequent changes were also studied. When these findings were compared to studies performed in other populations it was concluded that ages and order of primary tooth eruption in Spanish children are similar to those found in other populations.