In this study, we examined the accuracy of theLanguage ENvironment Analysis (LENA) system inEuropean French. LENA is a digital recording device withsoftware that facilitates the collection and analysis of audiorecordings from young children, providing automated measuresof the speech overheard and produced by the child.Eighteen native French-speaking children, who were dividedinto six age groups ranging from 3 to 48 months old, wererecorded about 10–16 h per day, three days a week. A total of324 samples (six 10-min chunks of recordings) were selectedand then transcribed according to the CHAT format. Simpleand mixed linear models between the LENA and human adultword count (AWC) and child vocalization count (CVC) estimateswere performed, to determine to what extent the automaticand the human methods agreed. Both the AWC andCVC estimates were very reliable (r = .64 and .71, respectively)for the 324 samples. When controlling the random factorsof participants and recordings, 1 h was sufficient to obtain areliable sample. It was, however, found that two age groups(7–12 months and 13–18 months) had a significant effect onthe AWC data and that the second day of recording had asignificant effect on the CVC data. When noise-related factorswere added to the model, only a significant effect of signal-tonoiseratio was found on the AWC data. All of these findingsand their clinical implications are discussed, providing strongsupport for the reliability of LENA in French.