In 121 women attending the infertility clinic between 1978 and 1982, 127 cycles with luteal phases of 10 days or more were investigated by a complete basal body temperature (BBT) chart, three plasma progesterone assays taken between 11 and 4 days before menses, and a dated endometrial biopsy (EB) taken at the time of the last blood sample. All parameters were normal in 78 women (64.4%) categorized as group I 'normal luteal phases (NLP)'. There were some discordances between the three parameters in the remaining 43 women: 8 had normal BBT but low progesterone levels and delayed EB. They form group II 'inadequate luteal phases'. 29 women (23.9%) had delayed EB despite normal progesterone levels: forming group III 'dysharmonic luteal phases (DLP)'. 6 women had advanced EB and normal progesterone levels: group IV. Apart from endometrial maturation, there was no difference between NLP and DLP, neither in clinical parameters (length of the follicular phase, date and duration of the thermal shift, length of the luteal phase), nor in progesterone levels. Fertilization occurred in four DLP biopsied cycles: pregnancies went normally to term, giving birth to normal babies. Therefore, the DLP syndrome, characterized by normal midluteal progesterone levels and a delayed endometrial development, is not incompatible with normal nidation and gestation.