1783 modal-falsetto register breaks and 853 falsetto-modal register breaks, produced by seven untrained adult male subjects, were recorded and analyzed with respect to jumps in fundamental frequency and sound pressure level (SPL) using a computer phonetograph. SPL and relative positions of modal and falsetto registers were the most important factors underlying the results. Whereas sub- or supraglottal coupling certainly cannot explain the results, models of intrinsic non-linear behavior of the vocal folds may need to be extended for explanations of breaks outside the overlap area of the two registers.