Infants in an orphanage who live in an underprivileged environment show delayed gross motor development; however longitudinal investigations of gross motor development in orphaned infants are limited. This study aimed to assess the variability of gross motor development of orphaned infants using a longitudinal observation. The gross motor development of 11 infants aged 1.5 months was assessed monthly until 11.5 months of age using the Alberta Infant Motor Scale. Infants showed instability of gross motor development. The total mean range of gross motor percentile was 55.4 (SD, 18.6; 95% confidence interval = 42.9-68.0). Thirty-six per cent of infants had little fluctuation of gross motor percentile that was below the 50th percentile across 11 assessments. Infants in orphanages display less instability of gross motor percentile. Orphaned infants, especially those with biological risk factors, should have their gross motor development monitored longitudinally during the first year of life.