Abstract: A study was conducted at Jimma (southwest Ethiopia) to develop simple method of estimating the optimum harvest time of fruits of six avocado cultivars. Fruit samples were collected six, seven, eight and nine months after flowering. At each harvest, physical measurements of the fruit samples were recorded and the fruit length-to-width ratio (L w^-1), fruit weight-to-length ratio (m L^-1) and equivalent diameter (d) were determined. The fruit samples were then allowed to ripe at ambient conditions. The dry matter and oil contents of the juice made from the ripe fruits were determined at each harvest date for respective cultivars. Oil content was highly significantly (p<0.001) influenced by the cultivars and harvesting dates compared. Dry matter content of fruits significantly differed among cultivars (p<0.05) and harvesting dates (p<0.01). Increased oil and dry matter contents were observed towards the later harvest dates. The cultivar Bacon recorded the highest mean oil content ( = 19.44±0.73%) while the lowest was obtained from the cultivar Pinkerton ( = 15.30±0.73%). The results revealed that harvest date could be a more reliable index of optimum maturity. No significant relationship was found between oil and dry matter contents; and the length-to-width ratio and the equivalent diameter. However, a significant correlation (α = 0.01) was observed between the oil content and the fruit weight-to-length ratio (m L^-1) at various stages of maturity. This physical parameter could be used as a simple method (maturity index) for the determination of time of harvest for optimum oil content of avocado fruit.