Objective: To assess the speaker-discriminatory potential of a set of fundamental frequency estimates in intraidentical twin pair comparisons and cross-pair comparisons (i.e., among all speakers). Participants: A total of 20 Brazilian Portuguese speakers of the same dialect, namely 10 male identical twin pairs aged between 19 and 35, were recruited. Method: the participants were recorded directly through professional microphones while taking part in a spontaneous dialogue over mobile phones. Acoustic measurements were performed in connected speech samples, and in lengthened vowels, at least 160 ms long produced during spontaneous speech. Results: f 0 baseline, central tendency, and extreme values were found mostly discriminatory in intra-twin pair and cross-pair comparisons. These were also the estimates displaying the largest effect sizes. Overall, only three identical twins were found statistically different regarding their f 0 patterns in connected speech, but not for lengthened vowel-based f 0 metrics. Estimates of f 0 variation and modulation were found the least discriminatory across speakers, which may signal the control of speaking style and dialect on dynamic patterns of f 0. Concerning system performance, the base value of f 0 (f 0 baseline) was found the most reliable metric, displaying the lowest equal error rate (EER). Conclusions: the outcomes suggest that, although identical twins were very closely related regarding their f 0 patterns, some pairs could still be differentiated acoustically, only in connected speech. Such findings reinforce the relevance of analyzing long-term f 0 metrics for speaker comparison purposes, with particular consideration to f 0 baseline. Furthermore, f 0 differences across subjects were suggested as more expressive in connected speech than in lengthened vowels.