Tonal identity and tonal variation in Mandarin have been the focus of intensive research that has long sought to bring out the underlying causes of variations in realized pitch values. Included among the variables studied in tonal variation are syntactic, contextual, emotional, and interactional influences. In the current study, we present results of our comparative research into tonal pitch variation in read speech and spontaneous Mandarin conversations. We acoustically and quantitatively characterize differences in the degree of pitch variability of these two modes of speech, and we present our results on tonal variability, as well as the influence of tone sequencing, syllable amplitude, and contextual factors on realized tonal shape. We show that, although tones are manifested in great diversity of pitch in spontaneous speech, there is a consistency of pitch shape that is dependent on tonal lexical identity.