The　stem　cells　of　neurogenesis　and　carcinogenesis　share　many　properties,　including　proliferative　rate,　an　extensive　replicative　potential,　the　potential　to　generate　different　cell　types　of　a　given　tissue,　and　an　ability　to　independently　migrate　to　a　damaged　area.　This　is　also　evidenced　by　the　common　molecular　principles　regulating　key　processes　associated　with　cell　division　and　apoptosis.　Autosomal　recessive　primary　microcephaly　(MCPH)　is　a　neurogenic　mitotic　disorder　that　is　characterized　by　decreased　brain　size　and　mental　retardation.　Until　now,　a　total　of　25　genes　have　been　identified　that　are　known　to　be　associated　with　MCPH.　The　inactivation　(yin)　of　most　MCPH　genes　leads　to　neurogenesis　defects,　while　the　upregulation　(yang)　of　some　MCPH　genes　is　associated　with　different　kinds　of　carcinogenesis.　Here,　we　try　to　summarize　the　roles　of　MCPH　genes　in　these　two　diseases　and　explore　the　underlying　mechanisms,　which　will　help　us　to　explore　new,　attractive　approaches　to　targeting　tumor　cells　that　are　resistant　to　the　current　therapies.