The present study examined the relative contribution of bottom-up word identification and top-down sentence-level constraints in facilitating the reading of text printed without between-word spacing. We compared reading of grammatically correct sentences and shuffled versions of the same words presented both with normal spacing and without spaces. We found that reading was hampered by removing sentence structure as well as by removing spaces. A significantly greater impact of sentence structure when reading unspaced text was found in probe word identification accuracies and total viewing times per word, whereas the impact of sentence structure on the probability of making a regressive eye movement was greater when reading normally spaced text. Crucially, we also found that the length of the currently fixated word determined the amplitude of forward saccades leaving that word during the reading of unspaced text. We conclude that the relative ease with which skilled readers can read unspaced text is due to a combination of an increased use of bottom-up word identification in guiding the timing and targeting of eye movements, plus an increased interactivity between word identification and sentence level processing.