A total of 8,684 first-lactation records produced in the region in the dairying seasons 1966-67 to 1972-1973, inclusive were assembled. Based on weighted and unweighted intra-sire regressions of progeny performance (deviation from within and within-year contemporary average) on time, a series of estimates of the genetic trend in production for the period were obtained. Variable estimates, allied with large standard precluded reliable conclusions on the nature of the genew By applying a mixed model solution method of sire-eva but only to restricted sub-sample of the data (2,155 records breeding values of 47 sires were estimated unbiased by The numbers of records involved were too few to allow a comparison of these estimates with estimates of the f the same sires obtained by the Farm Production D N.Z. Dairy Board using its method of sire evaluation. Based on variance component estimated obtained of Henderson's Method I, heritability of milk yield and was estimated to be 0.43 and 0.36 respectively. The agree well with estimates reported elsewhere. Additional estimates of the genetic trend were obtaine dregressing the solutions for the fixed effects (sire-group of the sire evaluation model on time.