This paper addresses the problem of infants' cry fundamental frequency estimation. The fundamental frequency is estimated using a modified simple inverse filtering tracking (SIFT) algorithm. The performance of the modified SIFT is studied using a real database of infants' cry. It is shown that the algorithm is capable of overcoming the problem of under-estimation and over-estimation of the cry fundamental frequency, with an estimation accuracy of 6.15% and 3.75%, for hyperphonated and phonated cry segments, respectively. Some typical examples of the fundamental frequency contour in typical cases of pathological and healthy cry signals are presented and discussed.