Small and medium businesses (SMBs) have caught tablet fever, according to the results of an NPD survey fielded in September and released Thursday.

Among these SMBs (defined as firms with fewer than 1,000 employees), 73% plan to purchase tablets in 2012, up from 68% three months earlier. And over the next 12 months they plan to spend an average of $21,000 on the devices.

Among larger firms (501 t0 999 employees), 89% plan to buy an average of $39,000 worth of tablet computers.

Among the smallest businesses (fewer than 50 employees), the percentage planning to buy and the amount they plan to spend are considerably lower (54% and less than $2,000, respectively).

Among both groups, however, Apple (AAPL) is likely to be the prime beneficiary, according to NPD’s Stephen Baker.

“The iPad, just as it is in the consumer market, is synonymous for ‘Tablet’ in the business market,” he wrote in Thursday’s e-mailed press release, “leaving Apple poised to take advantage of the increased spending intentions of these SMBs. NPD’s research shows that iPad purchase preference is higher among larger firms than smaller ones, which is an important indicator that Apple is gaining traction far outside its typical consumer space.”