Arithmetic is commonly taught through timed practice and drill, yet little research exists to guide optimal practice structure. This study investigated the effects of distributed practice and time pressure on the acquisition and retention of arithmetic facts. Following a pretest, adult participants (n = 211) were randomly assigned to learn unfamiliar times tables (17 and 19) in one of ten conditions in a 5 (spacing: daily, every other day, weekly, every 10 days, every other week) x 2 (time pressure: timed or untimed) factorial design. After the learning phase, retention tests were given to measure both accuracy and response time immediately, after a ten-day delay, and at the end of semester. Time pressure during learning elevated participants' perceived stress. It also led to faster response times during testing when learning was spaced daily and every other day, but slower response times for all other spacings. These patterns were reversed in the absence of time pressure during learning. While timed and untimed practice during learning led to similar forgetting of practiced facts over time, untimed practice allowed participants to gradually improve on unpracticed facts and conceptually related facts across test phases. Ultimately, distributed practice and time pressure may interact in complex ways to affect the learning and retention of arithmetic facts, and the effects shown in previous studies using verbal material (e.g., narrative texts, word lists) may not generalize to arithmetic.