Controlled pollinations and allozyme markers were used to compare mating system parameters among three populations of the rare woodland shrub Daviesia suaveolens Crisp. and five populations of its common relative D. mimosoides R. Br. Pollination results show that both species require a vector to facilitate pollination and have strong self-incompatibility mechanisms. Multilocus estimates of outcrossing rates confirm this, with all populations being highly outcrossed (D. suaveolens tm=0.78−1.0; D. mimosoides tm=0.71−0.96). Smaller and less dense D. mimosoides populations had higher correlations of outcrossed paternity than larger ones. The divergence of pollen pool allele frequencies from population frequencies was greater in smaller populations than in larger ones, in keeping with a lower effective size of the male source. Regression analyses generally failed to show effects of either plant size or local flowering environment on estimates of single-plant outcrossing rates. Most variation in these rates probably reflects the combined effects of sampling error, correlated mating and the influence of marker diversity on outcross detectability.