The purpose of this study was to compare the effect of the Latham-Millard presurgical orthopedics, gingivoperiosteoplasty, and lip adhesion protocol with conservative treatment (nonpresurgical orthopedics without gingivoperiosteoplasty) for palatal and dental occlusion in complete bilateral and complete unilateral cleft lip and palate. All patients were from the South Florida Cleft Palate Clinic. A retrospective dental occlusal study was conducted using serial dental casts that had been taken of patients from birth to 12 years of age. All surgical procedures, except for the secondary alveolar bone grafts in the conservative, nonpresurgical orthopedics group, were performed by D. Ralph Millard, Jr. Ralph Latham supervised the presurgical orthopedics cases. Samuel Berkowitz collected and analyzed all the serial records from 1960 to 1996. Among the patients with complete unilateral cleft lip and palate, 30 patients were treated with presurgical orthopedics, gingivoperiosteoplasty, and lip adhesion (the Latham-Millard protocol) and 51 patients were treated conservatively (i.e., nonpresurgical orthopedics without gingivoperiosteoplasty). Among the patients with complete bilateral cleft lip and palate, 21 patients were treated with the Latham-Millard protocol and 49 patients were treated conservatively. Conservative treatment was performed between 1960 and 1980. In patients with bilateral cleft lip and palate, a head bonnet with an elastic strip was used to ventroflex the protruding premaxilla. In all patients (unilateral and bilateral cleft), lip adhesion was performed at 3 months followed by definitive lip surgery at 6 to 8 months and palatal cleft closure between 18 and 24 months of age, in most cases. The Latham-Millard procedure was performed from 1980 to 1996; in bilateral cleft patients, it involved the use of a fixed palatal orthopedic appliance to bodily retract the protruding premaxilla and align it within the alveolar segments soon after birth. In all patients (unilateral and bilateral cleft), palatal alignment was also followed by gingivoperiosteoplasty and lip adhesion. Definitive lip surgery was performed between 6 and 8 months of age, and palatal closure was performed between 8 and 24 months of age using the von Langenbeck procedure with a modified vomer flap. All of the study participants had cleft lips and palates of either the unilateral or bilateral type; the unilateral and bilateral groups were further subdivided based on whether they had received the Latham-Millard protocol or the conservative treatment. It was then determined how many in each of these four basic groups had either anterior or buccal crossbites at four different age levels, when they were approximately 3, 6, 9, and 12 years of age. Although several children entered the study at or just before age 6, every patient in the 9-year-old and 12-year-old sample groups had been in the 6-year-old group and all of the 12-year-olds had been included in the immediate preceding age sample. Two-by-two chi-square tests were carried out within each cleft type (unilateral or bilateral) at each of the four age levels separately, to test whether the treatment groups (protocol versus conservative) differed in the frequency of cases with a given kind of crossbite (rather than not having that kind of crossbite). At every age level, a greater percentage of patients treated with the Latham-Millard protocol developed crossbites than did those treated more conservatively. This difference existed for both the anterior and buccal crossbites and for both unilateral and bilateral clefts. Chi-square tests of the treatment differences in crossbite frequency showed that in three quarters of the Latham-Millard protocol versus conservative treatment comparisons (12 out of 16), a significantly greater frequency of crossbite cases occurred after the Latham-Millard protocol treatment as compared with after the conservative procedure. The chi-square values for the differences in outcome between the two kinds of treatment procedures were greater for the anterior crossbites than for the buccal crossbites, suggesting that the Latham-Millard protocol, relative to the conservative method, was more likely to have an adverse effect on the anterior crossbites than on the buccal crossbites. For those patients born with a bilateral cleft, the differences in crossbite frequency between the protocol and the conservative treatment were statistically significant for patients with an anterior crossbite but not for patients with a buccal crossbite. The analysis shows that in complete bilateral and unilateral cleft lip and palate, the frequency of the anterior crossbite and (except for ages 3 and 12) the buccal crossbite is significantly higher with the Latham-Millard presurgical orthopedics, gingivoperiosteoplasty, and lip adhesion protocol compared with the conservative, nonpresurgical orthopedics without gingivoperiosteoplasty treatment. The exception in the bilateral buccal case may be attributed to the small experimental sample size, which brings down the confidence level.