The temporal pattern in transmission of the pine wood nematode, Bursaphelenchus xylophilus, from its vector, the Japanese pine sawyer, Monochamus alternatus, to pine trees was investigated. Forty adult sawyers were raised on excised pine twigs to measure the number of transmitted nematodes and the area of bark consumed by a sawyer at 5-day intervals. Females fed on more food than males. The number of nematodes carried by the sawyer at emergence had no effect on its food consumption per unit time. Thirty-three sawyers showed unimodal nematode-transmission curves and two showed L-shaped curves. The averaged transmission curves of the sawyers carrying more than 10, 000, 1, 000 to 9, 999, and 100 to 999 nematodes had one peak of about 1, 500, about 370, and 38 nematodes per 5 days, respectively, which appeared during a period from the 20th to 35th day after emergence of the sawyer. No peak was obvious in the transmission curve of the sawyers carrying less than 100 nematodes. The percentage of nematodes remaining within a dead sawyer tended to increase as the initial number of nematodes carried increased.