We report solid-state, optically pumped poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), distributed feedback lasers that operate in the green-yellow spectral region, previously unaddressed with conjugated polymer gain media. The lasers were fabricated by spin coating F8BT (the gain medium) onto one-dimensional gratings patterned in silica substrates. The emission wavelength could be selected to lie within the range from 558 to 591 nm by controlling the F8BT film thickness and grating periodicity. The minimum lasing threshold of 6.5 nJ per pump pulse (10 ns, 10 Hz, 450 nm) was achieved for a 350 nm spatial period grating with a 180 nm thickness F8BT film. The corresponding emission wavelength was 573 nm and the laser slope efficiency was a relatively high 3%. © 2005 American Institute of Physics.