The aim of this study was to collect data concerning the sensitivity of 2nd-6th grade Spanish-speaking children towards orthographic regularities. In a first experiment, children were asked to spell words that begin with /b/, a sound that is inconsistently spelled "b" or "v", depending on the lexeme. Low frequency words were used to reduce the use of lexical information in spelling. In Spanish, the frequency of graphemes "b" and "v" depends on the following vowel; for example, in initial position, the bigram "vi" is more frequent than "bi" while "vu" is less frequent than "bu". Evidence concerning the use of sublexical regularities in English and French--opaque orthographic systems--is already available. The question was whether such knowledge also applies in a more transparent system like Spanish, in which a phonologically based strategy is quite efficient. The main finding was that participants' spelling strongly depended on the relative frequency of bigrams. This was already evident in second graders' spelling and increased with schooling. In Experiment 2 these results were confirmed using pseudo-words. The results exclude a functional view of spelling, which supposes that orthographic resources are not used to spell in consistent orthographic systems, since phonologically based mechanisms are sufficient to override any others.