Field capacity is a widely used concept for irrigation management, but its definition is still controversial. Field capacity has been recognized by soil physicists a process of free drainage and it can not be defined as an intrinsic properties of the soil. To investigate further the meaning of field capacity, soil water content to a depth of 1 m and matrix flow by Darcy’s law at 1-m depth were measured and calculated every 30 minute for 1997 and 1998 at a maize-Chinese cabbage cropping field. Matric potential profiles with depth of a soybean field were also measured at a heavy rain event in 1991. The field soil is a well-drained volcanic ash soil. As the matrix flow is influenced by soil water content profiles during rain event and rainfall distribution pattern, the rain events whose amounts at the final day of consecutive rainy days were more than 10 mm/d, and brought the maximum values of matrix flow exceeding 5 mm/d at 1-m depth on the day following the rainfall were applied for discussing field capacity. When soil water conditions on the second day after the rainfall were applied as a field capacity, the matrix flow was 4 mm/d, and the hydraulic conductivity and the hydraulic gradient at 1-m depth were approximately 1X10-5 cm/s and 0.5, respectively. The amount of water stored to a depth of 1 m was 620 mm and the matric potential in the subsoil ranged between -50 to —100 cm. The matrix flow of 4 mm/d was very small compared to 620 mm water stored to a depth of 1 m. Although free drainage was still lasting on the second day after heavy rain events, the day can be applied as the field capacity for well-drained volcanic ash soils.