A series of 5',5-disubstituted 3-biphenylylacetic acids (5a-n) and several alpha-methyl derivatives (5o-v) were prepared as analogues of a newly developed nonsteroidal antiinflammatory agent, 5'-chloro-5-methoxy-3-biphenylylacetic acid [1 (DKA-9), R = 4-C1Ph; R' = Me], and evaluated for antiinflammatory and analgesic activities using both carrageenan rat paw edema and AcOH writhing assays. Among them, 5-fluoro-3-biphenylylacetic acid (5m) showed the highest antiinflammatory activity, while 2-(3-biphenylyl)propionic acid (5o) showed the highest analgesic activity. However, they were less potent than 1 (R = 4-C1Ph; R' = Me) in these assays.