Low delay (about 2 ms) CELP structures are studied for digital coding of speech at 8, 9,6 and 16 kbit/s. Seven backward adaptative prediction algorithms are investigated. These algorithms are used for adapting the short-term prediction filter and the weighting filter in low delay CELP coders. One algorithm uses block adaptation and the others are recursive with transversal and lattice structures. Comparisons are based on the objective measures of signal to noise ratio, segmental signal to noise ratio and a frequency weighted signal to noise and on subjective results obtained from informal listening tests.