In Mandarin, Fundamental Frequency (F0) peak delay has been reported to occur frequently in the rising (R) tone or high (H) tone succeeding by a low (L) tone. Its occurrence was ascribed to articulatory constraints within a conflicting tonal context: a high offset target followed by a low onset target. To further examine the underlying mechanism of the phenomenon, the current study tests the possibility that valley delay, as opposed to peak delay, may occur in an L+ H tonal context; and peak or valley delay may also occur within a compatible tonal context where adjacent tonal values are identical or similar. An experiment was done on Annotated Speech Corpus of Chinese Discourse to investigate the frequency of occurrence and amount of peak and valley delay. The results indicated that: F0 peak and valley delay frequently occurred in both conflicting and compatible tonal contexts; the phenomenon was found extensively in R tone and F (falling) tone, but barely in H tone and L tone. The findings suggest that while peak or valley delay is partially due to articulatory constraints in certain tonal contexts, the speakers’ active effort-distribution strategy based on economical principle is also behind the phenomenon.