Purpose: The aims of this study were to investigate the principal reasons for untimely loss of primary molars and to evaluate the risk factors of early primary molar loss in children aged four to nine years. Materials and Methods: 1150 untimely lost primary molars were analyzed from 546 patients. The early loss of primary molars was analyzed in relation to age, sex, dmf (t), DMF (T) scores, toothbrushing frequency, history of treatment and maternal education. The data were converted to SPSS format. Pearson Chi-square test was used for statistical analysis. Results: Among the investigated subjects, 15.2% of children reported regular toothbrushing. Only 23.1% of subjects had a history of treatment before the tooth extraction and 33% of mothers had a low education level. Untimely loss of primary molars due to pain, caries and sepsis were 30.2%, 31% and 38.8%, respectively. The frequency of 'only one primary molar loss' was significantly higher in group 1 (p 0.05), however the frequency of 'more than one primary molar loss' for group 2 was more than group 1 (p 0.05). Irregular toothbrushing for the children in group 2 was found significantly high than in group 1 (p 0.05). Irregular toothbrushing was associated with number of early primary molar loss in group 2 (p 0.05). The level of maternal education was associated with dmf (t) scores (p 0.05). The caries incidence was associated with number of early primary molar loss in both groups (p 0.05). The mean number of treated teeth before extraction for group 2 was significantly higher than for group 1 (p 0.05). Conclusion: Results of this study suggested that irregular toothbrushing, high dmf (t) scores and untreatment of carious primary molars were significant risk factors in early loss of primary molars. Every effort must be taken into account in restoring rather than extracting carious teeth. Palabras clave: early tooth loss, primary molars