Deaf and hearing college students' mean reaction times (RTs) were compared on a mental calculation task in which they had to verify the accuracy of solutions to addition and multiplication problems. The deaf students were divided into higher and lower readers. Higher deaf readers and hearing students had similar RTs and accuracy on addition problems; their RTs were greater in the voicing interference mode than in the manual tapping interference mode. The lower deaf readers showed no RT differences between the two interference modes and had consistently lower RT performance and score accuracy across the verification tasks. On the verification task for multiplication problems, all participants showed a greater RT effect for manual tapping. The lower deaf readers were significantly less accurate on multiplication problems. (Contains 4 tables and 1 figure.)