The effect of two training procedures on the improvement of reading accuracy in poor readers was examined in relation to their initial reading level. A randomized controlled trial was conducted with 60 poor readers. Poor readers were assigned to a control group that received no training, or one of two training conditions. One training concentrated on the words the children read correctly (successes), the other on the words they read incorrectly (failures). They repeatedly read bisyllabic Dutch words, half of the training words involving context-sensitive spelling rules (vowel degemination or consonant gemination). Some children repeatedly read their successes, others their failures. The training used a computerized flashcards format. The exposure duration of the words was varied to maintain the accuracy rate at a constant level. In general, children who received training improved their reading accuracy and reading speed of trained words, and reading accuracy of untrained words, more than the control group. Which training focus is superior, depends on the reading level of the child and the type of words used. For children with a low initial reading level, to improve reading accuracy of bisyllabic words that follow context-sensitive spelling rules, a training focus on failures was superior over a training focus on successes. For children with a high initial reading level, improvement of reading speed was largest in a training on successes. Evidently, the improvement of word reading skills depends both on the children's level of reading competence and on the type of training.