The ingestion of plastic was recorded for 36 of 60 seabird species sampled in the southern hemisphere (mostly off southern Africa). Biases of different sampling techniques were considered. Plastic was most frequent in procellariiforms, notably Blue Petrels, Great Shearwaters, White-faced Storm-petrels and Pintado Petrels. Particles were compared with those found at sea. The size of ingested particles was related to body size, and this affected the proportions of plastic types ingested. Pale particles were underrepresented, suggesting selection for darker-coloured particles. Small species were less colour-selective and exhibited a higher incidence of plastic ingestion than did large species. The incidence of ingested plastic was directly related to foraging technique and inversely related to the frequency of egestion of indigestible stomach contents. Secondary ingestion of plastic through contaminated prey was important in only one species sampled.