This study investigates fact retrieval deficits in low-achieving children and children with mathematical learning disabilities (MLD). Using four years of mathematics achievement data, the researchers identified groups of typically achieving children (n = 101), low-achieving children with mild (LA–mild fact retrieval; n = 97) and severe (LA–severe fact retrieval; n = 18) fact retrieval deficits, and children with MLD (n = 15). Multilevel models were used to compare the development of retrieval competence from second to fourth grade with competence in executing arithmetic procedures, fluency in processing quantities represented by Arabic numerals and sets of objects, and representing quantity on a number line. The study found that children with severe fact retrieval deficits showed deficits as debilitating as those of children with MLD, with less improvement across grades. These deficits were characterized by retrieval of counting string associates while attempting to remember addition facts, suggesting poor inhibition of irrelevant information during retrieval. This indicates a specific working memory deficit not captured by typical working memory tasks. These deficits were not related to procedural competence or performance on other mathematical tasks, nor to verbal or nonverbal intelligence, reading ability, or processing speed. The study also examined number line representations and number sets. Children with MLD relied more on the natural representational system, showing more compressed magnitude representations than typically achieving children. LA children showed similar patterns but with less severe deficits. The study found that children with MLD had lower d-prime scores in first grade, indicating deficits in basic number processing competencies. The study compared the fact retrieval deficits of children with MLD and LA children to determine if their developmental trajectories and error patterns were similar or different. The results showed that children with MLD and LA–severe fact retrieval children had similar deficits, with the latter showing less improvement across grades. The study also found that children with MLD used finger counting more frequently and made more counting errors than other groups. The study concluded that children with MLD and LA–severe fact retrieval children had similar deficits in fact retrieval, with the latter showing less improvement across grades. The study also found that children with MLD used verbal counting more frequently and made more counting errors than other groups. The study highlights the importance of understanding the specific nature of mathematical deficits in children with learning disabilities.This study investigates fact retrieval deficits in low-achieving children and children with mathematical learning disabilities (MLD). Using four years of mathematics achievement data, the researchers identified groups of typically achieving children (n = 101), low-achieving children with mild (LA–mild fact retrieval; n = 97) and severe (LA–severe fact retrieval; n = 18) fact retrieval deficits, and children with MLD (n = 15). Multilevel models were used to compare the development of retrieval competence from second to fourth grade with competence in executing arithmetic procedures, fluency in processing quantities represented by Arabic numerals and sets of objects, and representing quantity on a number line. The study found that children with severe fact retrieval deficits showed deficits as debilitating as those of children with MLD, with less improvement across grades. These deficits were characterized by retrieval of counting string associates while attempting to remember addition facts, suggesting poor inhibition of irrelevant information during retrieval. This indicates a specific working memory deficit not captured by typical working memory tasks. These deficits were not related to procedural competence or performance on other mathematical tasks, nor to verbal or nonverbal intelligence, reading ability, or processing speed. The study also examined number line representations and number sets. Children with MLD relied more on the natural representational system, showing more compressed magnitude representations than typically achieving children. LA children showed similar patterns but with less severe deficits. The study found that children with MLD had lower d-prime scores in first grade, indicating deficits in basic number processing competencies. The study compared the fact retrieval deficits of children with MLD and LA children to determine if their developmental trajectories and error patterns were similar or different. The results showed that children with MLD and LA–severe fact retrieval children had similar deficits, with the latter showing less improvement across grades. The study also found that children with MLD used finger counting more frequently and made more counting errors than other groups. The study concluded that children with MLD and LA–severe fact retrieval children had similar deficits in fact retrieval, with the latter showing less improvement across grades. The study also found that children with MLD used verbal counting more frequently and made more counting errors than other groups. The study highlights the importance of understanding the specific nature of mathematical deficits in children with learning disabilities.