This trial was to determine if the widespread unthriftiness, nutrient deficiency symptoms, low production and poor ratooning observed in pineapple plantings were due to underfertilization or nematode damage, and the response of nematode-damaged plants to increasing N-P-K fertilization. A plot heavily i?ifested with Helicotylenchus multicinetus and Pratylenchus sp. was fumigated with a DD/DBCP mixture before and treated with phenamiphos after planting. A 12-8-30 N-P-K fertilizer was applied to the Smooth Cayenne, 3ed Spanish or Sugar Loaf varieties at 560, 1120 or 168O kg/ha/year. At 5, 9, 13 and 17 months, plants of the 3 varieties in the nematicide-treated plots were significantly "bigger, had much longer roots and significantly less of them were nutrient deficient compared with infested plots. Many more plants in the nematicide-treated areas bore and fruits were significantly larger than in the untreated plots. In the ratoon crop, the majority of plants in the untreated plots were nutrient deficient compared with significantly less in the nematicide-treated plots. More and larger fruits were borne, particularly with the Sugar Loaf variety, in the nematicide-treated plots. There was no influence of increasing fertilization whether in nematicide- treated or untreated plots in either crop for any variety. Nematode-damaged pineapple plants were nutrient deficient and grew and produced poorly even with adequate fertilization. The greatest responses to nematode suppression were observed with the Smooth Cayenne variety.