A planetary gear train of an automatic transmission for vehicles may include an input shaft receiving torque of an engine, an output shaft outputting changed torque, a first planetary gear set, a second planetary gear set, a third planetary gear set, a fourth planetary gear set, a first rotational shaft selectively connected to a transmission housing, a second rotational shaft directly connected to the input shaft, a third rotational shaft, a fourth rotational shaft, a fifth rotational shaft selectively connected to the first rotational shaft or the second rotational shaft, a sixth rotational shaft directly connected to the output shaft, a seventh rotational shaft selectively connected to the transmission housing, an eighth rotational shaft selectively connected to the fourth rotational shaft or the fifth rotational shaft, and six friction elements interposed between the rotational shafts, or between at least one rotational shaft and the transmission housing to connect selectively.